Body Controller Fault Diagnosis

Diagnostic System Check - Vehicle

1. Before proceeding with the diagnosis, you must make sure that none of the following preliminary inspections / checks will show the cause of the vehicle's malfunction.

• Make sure the battery is fully charged
• Make sure the battery cables are clean and fasteners are tight.
• Check for blown fuses
• Ensure ground wires are clean, fasteners are tight and ground wires are properly connected.
• Inspect easily accessible systems or visible parts of systems for obvious signs of damage or conditions that could lead to a malfunction.
• Inspect aftermarket equipment that may interfere with system operation.
• Find service bulletins related to the problem.

2. Install the diagnostic tool. Verify that the scan tool is receiving power.

3. Turn on the ignition, engine off, check communication with all controllers on the vehicle.

Important: Open the driver's door to prevent activation of the auxiliary power hold mode (RAP) during this check. During this test, you can start the engine. Turn off the engine as soon as the power mode has been checked when starting the engine.

4. Using the scan tool, access the body controller power mode parameter list. Make sure that all parameters listed in the following table correspond to the position of the key in the ignition lock. The following PMM power mode settings table illustrates the correct state of these settings (chains) in the respective positions of the ignition switch. The circuits corresponding to the parameters are indicated in brackets.


5. Turn on the ignition, observe the safety indicator. The safety light should remain on after the vehicle lamp test is completed.

6. Try to start the engine. Make sure the engine turns over.

7. Try to start the engine. Make sure the engine starts and runs.

Important: Do not clear any DTCs unless directed to do so by the diagnostic procedure.

Important: If any trouble codes are associated with the power plant, select the item "Gather Information", to store DTC information using the scan tool.

PMM Power Mode Options

Ignition switch position	Current Power Mode	Ignition Off/Run/Start (shutdown/run/start voltage circuits)	Ignition Auxiliary/Start (auxiliary voltage circuit)	Ignition work/start (voltage circuit "Ignition 1")
Off, key out	Turned off	Key out/auxiliary	Inactive	Inactive
Off, key inserted (LOCK - locked)	Turned off	Key inserted/disabled	Inactive	Inactive
ACC	Auxiliary	Key inserted/ACC (auxiliary)	Active	Inactive
ON	Job	Job	Active	Active
START	Start request	Start (turning)	Inactive	Active

List of diagnostic trouble codes (DTC)

DTC code	Description	SUBSYSTEM
B0283	Heated rear window circuit	HEATING, VENTILATION AND AIR CONDITIONING SYSTEM
B0981	Short circuit on the mass of the switch of a winter mode of a transmission	POWER POINT
B1000	Operation of the electronic control controller (ECU), special memory failure	DESIGN
B1000	Operation of the electronic control controller (ECU), RAM integrity	DESIGN
B1000	Operation of the electronic control controller (ECU), ROM integrity	DESIGN
B1000	Operation of the electronic control controller (ECU), EEPROM integrity	DESIGN
B1001	Option configuration error - option not programmed	DESIGN
B1016	VIN not programmed	DESIGN
B1370	Ignition circuit short 1 device (ON and START) for battery voltage	DESIGN
B1370	Ignition circuit short 1 device (ON and START) to ground or break	DESIGN
B1380	AUXILIARY device ignition circuit short to battery voltage	DESIGN
B1380	AUXILIARY device ignition circuit short to ground or open	DESIGN
B1395	Device voltage reference circuit at output 1 - voltage below threshold	LIGHTING SYSTEM
B1395	Device voltage reference circuit at output 1 - voltage above threshold	LIGHTING SYSTEM
B1428	Ignition 1 Power Switch Relay Circuit	DESIGN
B1433	Ignition 2 Power Switch Relay Circuit	DESIGN
B1440	Power Mode Master Input Circuit Mismatch	DESIGN
B1441	Shorting the ignition circuits of the device OFF, OPERATION and START to battery voltage.	DESIGN
B1441	Device ignition circuits OFF, RUN, and START shorted to ground or open.	DESIGN
B1475	Auxiliary power holding circuit	DESIGN
B1480	Battery Discharge Protection Circuit	CHARGING SYSTEM
B1517	Battery voltage below threshold	CHARGING SYSTEM
B1517	Battery voltage above threshold	CHARGING SYSTEM
B2530	Front fog lamp control circuit	LIGHTING SYSTEM
B2545	reverse lamp circuit	LIGHTING SYSTEM
B2575	Headlight control circuit	LIGHTING SYSTEM
B257A	Headlight switch input mismatch	LIGHTING SYSTEM
B2580	High Beam Control Circuit	LIGHTING SYSTEM
B2585	Left Parking Light Control Circuit	LIGHTING SYSTEM
B2625	Pulse Width Modulation Output Circuit (PWM) display lighting adjustment	LIGHTING SYSTEM
B2645	The voltage in the ambient light sensor circuit is below the threshold	LIGHTING SYSTEM
B2645	The voltage in the ambient light sensor circuit is above the threshold	LIGHTING SYSTEM
B2705	Short circuit of a chain of an unblocking of a gear change on weight	POWER POINT
B2745	Traction control switch circuit short to ground	CHASSIS
B2750	Horn Relay Coil Circuit	AUXILIARY
B2924	Anti-theft sensor 3 signal circuit (slope etc.)	anti-theft system
B3089	Anti-theft sensor 1 signal circuit (concussion, penetration, etc.)	anti-theft system
B3130	All door unlock circuit	AUXILIARY
B3135	Locking chain for all doors	AUXILIARY
B3265	Trunk/Tailgate/Sliding Window Release Output Circuit	AUXILIARY
B3445	Brake light circuit	LIGHTING SYSTEM
B3622	Steering Wheel Controls Signal Circuit Group 1 - Voltage Above Threshold	DESIGN
B370C	Rain Sensor Intensity Signal Circuit	WIPERS AND WASHERS
B370D	Rain Sensor Mode Control Circuit	WIPERS AND WASHERS
B3715	Front Wiper Relay Control Circuit	WIPERS AND WASHERS
B3794	Cruise Control Function Request Circuit - Wrong Signal	POWER POINT
B3794	Cruise Control Function Request Circuit - Stuck Actuator	POWER POINT
B3812	Theft Deterrent Sensor Ground Circuit	anti-theft system
B3873	Front Washer Relay Circuit	WIPERS AND WASHERS
B3875	Wiper High Speed Relay Circuit	WIPERS AND WASHERS
B3922	Front wiper function selection circuit	WIPERS AND WASHERS
B3933	A/C evaporator temperature sensor circuit (A/C) - voltage above threshold	HEATING, VENTILATION AND AIR CONDITIONING SYSTEM
P0826	Upshift and downshift circuit - wrong signal	POWER POINT
P0826	Upshift and downshift chain - drive jammed	POWER POINT
U0073	Controller communication bus not working	DESIGN
U0100	Lost communication with ECM/PCM "A"	POWER POINT
U0101	Disruption of communication with TCM	POWER POINT
U0155	Disruption of communication with the instrument cluster controller (IPC)	DESIGN
U0164	Lost communication with body controller (BCM)	HEATING, VENTILATION AND AIR CONDITIONING SYSTEM
U1814	Circuit for enabling a high-speed communication line with the power plant	DESIGN
U2099	High Speed Link Enable Circuit	DESIGN

• body controller (BCM) detects a short to battery positive in the DEFOG relay control circuit when the body controller (BCM) trying to apply voltage to the relay.
• body controller (BCM) detects that the control circuit of the DEFOG relay is open.
• The described condition must be valid for more than 1 second.

• body controller (BCM) Stores fault code B0283 in memory.
• The heated glass will not work.

• The current fault code is cleared after the fault disappears.
• The fault code is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold without recurring the fault.

2. Check positive battery voltage at the coil side of the heated rear window relay. The coil side of the DEFOG relay is energized through fuse EF25 (10 A).
3. Test the control circuit side DEFOG relay circuit for faults causing DTC B0283.
4. Listen to the clicks when the DEFOG relay is activated. Issue a command to turn on and off. Repeat commands if necessary.
5. Check that the body controller (BCM) connected the glass heating relay to ground.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section «Diagnostic System Check - Vehicle» in the description of vehicle trouble codes.
2	Replace DEFOG relay (glass heating). Connect a test lamp between the supply circuit of the DEFOG relay from the EF25 fuse (10 A) and ground at the DEFOG relay socket. Switch on the ignition with the engine off. Does the control lamp light up?	-	Go to Step 3	Go to Step 8
3	Switch off the ignition. Test the DEFOG relay control circuit for a short to battery positive voltage or ground. Has the cause been found and fixed?	-	Go to Step 11	Go to Step 4
4	Connect a test lamp between the supply circuit of the DEFOG relay from the EF25 fuse (10 A) and the control circuit at the DEFOG relay socket. Switch on the ignition with the engine off. Using a scan tool, command the relay on and off. Does the control lamp light up and go out?	-	Go to Step 6	Go to Step 5
5	Test the control circuit of the DEFOG relay for an open. Has the cause been found and fixed?	-	Go to Step 11	Go to Step 7
6	Inspect the relay socket for loose connections or damaged terminals. Has the cause been found and fixed?	-	Go to Step 11	Go to Step 9
7	Check for a poor connection in the body controller wiring harness connector (BCM). Has the cause been found and fixed?	-	Go to Step 11	Go to Step 10
8	Repair a short to ground, broken contact or open circuit in the supply voltage circuit of fuse EF25 (10 A). Has the repair been completed?	-	Go to Step 11	-
9	Replace DEFOG relay (glass heating). Has the replacement been completed?	-	Go to Step 11	-
10	Replace body controller (BCM). Has the replacement been completed?	-	Go to Step 11	-
11	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 2	System OK

2. At this stage, the operation of the winter mode switch is checked.
3. This step tests the input voltage from the BCM to the winter mode switch.
6. At this stage, the integrity of the mass circuit is checked.

Step	Operation	Values	Yes	No
1	Install the diagnostic tool. Switch on the ignition with the engine off. Turn the winter mode switch on and off while monitoring the scan tool. Does the scan tool display ACTIVE when the switch is pressed for the first time and INACTIVE when the switch is pressed again?	-	Go to Section 9A, "Checking body wiring systems for intermittent faults and contact problems".	Go to Step 2
2	Disconnect the connector from the winter mode switch. Connect a fused jumper wire to the switch signal circuit at the switch connector. Does the scan tool indicate a parameter status change "Winter mode"?	-	Go to Step 7	Go to Step 3
3	Measure the voltage on the switch signal circuit at the switch connector. Does the measured value match the ignition voltage?	-	Go to Step 6	Go to Step 4
4	Measure the voltage on the body controller switch signal circuit (BCM). Does the measured value match the ignition voltage?	-	Go to Step 5	Go to Step 8
5	Check switch signal circuit for shorts. Has the cause been found and fixed?	-	Go to Step 9	Go to Section 9A, "Checking body wiring systems for intermittent faults and contact problems".
6	Check the ground circuit of the switch for shorts. Has the cause been found and fixed?	-	Go to Step 9	Go to Section 9A, "Checking body wiring systems for intermittent faults and contact problems".
7	Replace winter mode switch. Has the replacement been completed?	-	Go to Step 9	-
8	Replace BCM. Has the cause been found and fixed?	-	Go to Step 9	-
9	At the end of the repair, observe the parameter "Winter mode" on the screen of the diagnostic tool, alternately turning the switch on and off. Does the scan tool display ACTIVE when the switch is pressed for the first time and INACTIVE when the switch is pressed again?	-	System OK	Go to Step 1

• The current fault code is cleared after the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• This DTC can be stored in the DTC log without affecting the functionality of the controller.
• If the DTC is only logged and not issued as a current DTC, do not replace the controller.
• If a DTC is received as both current and logged, replace the controller that generated the DTC.

• The current fault code is cleared after the fault disappears.
• The fault code is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold without recurring the fault.

1. Program the airbag identification number into the body controller (BCM).
2. Read DTCs from the BCM. DTC B1001 should change status to logged.
• If the DTC remains current, replace the BCM.

• The current fault code is cleared after the fault disappears.
• The fault code is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold without recurring the fault.

1. Program the VIN information into the body controller (BCM).
2. Switch off the ignition, wait a few seconds and switch on the ignition.
3. Read DTCs from the BCM. DTC B1016 should change status to logged.
• If this DTC is received as current, replace the controller that generated this DTC.

• The ignition switch is in the OFF or ACC position.
• The ignition switch is in the START position.

• The ignition 1 voltage circuit is shorted to supply voltage for more than 2 seconds.
• Ignition 1 voltage circuit open for more than 2 seconds.
• Ignition voltage 1, auxiliary voltage or voltage circuit "off/work/start" closed to mass.
• Open or short to ground in the battery positive voltage circuit at the ignition switch.
• Break in the control circuit of the relay winding "work/start" (including relay coil and ground).

• The current fault code is cleared after the fault disappears.
• The fault code is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold without recurring the fault.

• A short to ground in the auxiliary wake-up circuit of the serial link will blow the fuse to the ignition switch. DTC U1814 should be current.
• Short to ground in the ignition voltage circuit 1 "work/start" on the start relay will blow the fuse on the ignition switch. DTC B1428 should be current.
• Power modes and control actions are determined by the BCM circuits. By comparing the displayed body controller power mode options in the list "Circuit/System Check" detects the presence of a power failure.

1. Inspect the ignition switch fuse for a blown one. The fuse must be good.
• If the fuse is blown, check the following circuits for a short to ground. If all circuits test normal, replace the BCM.
- Positive battery voltage on the ignition switch Auxiliary voltage - Voltage "off/work/start" - Ignition voltage 1
2. Disconnect the ignition switch connector.
3. Test positive battery voltage between the battery positive voltage circuit at the ignition switch and ground.
• If the voltage is lower than battery positive voltage, repair the open or high resistance in the circuit.
4. Check ignition switch parts.
• If the ignition switch is faulty, replace the ignition switch.
5. Ignition OFF, disconnect the C1 connector at the BCM, test for less than 1.0 V between the following BCM circuits and ground.
6. Remove the ignition key, test for less than 1.0 volts between the following BCM circuits and ground:
- Ignition switch resistor signal - Off/Run/Start - Auxiliary voltage Ignition voltage 1
• Above 1.0 V, repair the circuit for a short to voltage.
7. Test the resistance of the following circuits between the BCM and the ignition switch for less than 1.0 ohms:
- Ignition switch resistor signal - Off/Run/Start - Auxiliary voltage Ignition voltage 1
• If resistance is greater than 5 ohms, repair the open or high resistance in the circuit.
8. Test for infinite resistance between the ignition switch resistor signal circuit at the BCM and ground.
• If the resistance is not infinite, repair the short to ground in the signal circuit.
9. Replace BCM.

• The ignition switch is in the START position.
• Ignition switch is in the RUN position (JOB).

• Auxiliary voltage circuit shorted to supply voltage for more than 2 seconds.
• Ignition auxiliary voltage circuit open for more than 2 seconds.
• Ignition voltage 1, auxiliary voltage or voltage circuit "off/work/start" closed to mass.
• Open or short to ground in the battery positive voltage circuit at the ignition switch.

• The current fault code is cleared after the fault disappears.
• The fault code is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold without recurring the fault.

• A short to ground in the auxiliary wake-up circuit of the serial link will blow the fuse to the ignition switch. DTC U1814 should be current.
• Short to ground in the ignition voltage circuit 1 "work/start" on the start relay will blow the fuse on the ignition switch. DTC B1428 should be current.
• Power modes and control actions are determined by the BCM circuits. By comparing the displayed body controller power mode options in the list "Circuit/System Check" detects the presence of a power failure.

1. Inspect the ignition switch fuse for a blown one. The fuse must be good.
• If the fuse is blown, check the following circuits for a short to ground. If all circuits test normal, replace the BCM.
- Positive battery voltage on the ignition switch Auxiliary voltage - Voltage "off/work/start" - Ignition voltage 1
2. Disconnect the ignition switch connector.
3. Test positive battery voltage between the battery positive voltage circuit at the ignition switch and ground.
• If the voltage is lower than battery positive voltage, repair the open or high resistance in the circuit.
4. Check ignition switch parts.
• If the ignition switch is faulty, replace the ignition switch.
5. Ignition OFF, disconnect the C1 connector at the BCM, test for less than 1.0 V between the following BCM circuits and ground.
6. Remove the ignition key, test for less than 1.0 volts between the following BCM circuits and ground:
- Ignition switch resistor signal - Off/Run/Start - Auxiliary voltage Ignition voltage 1
• Above 1.0 V, repair the circuit for a short to voltage.
7. Test the resistance of the following circuits between the BCM and the ignition switch for less than 1.0 ohms:
- Ignition switch resistor signal - Off/Run/Start - Auxiliary voltage Ignition voltage 1
• If resistance is greater than 5 ohms, repair the open or high resistance in the circuit.
8. Test for infinite resistance between the ignition switch resistor signal circuit at the BCM and ground.
• If the resistance is not infinite, repair the short to ground in the signal circuit.
9. Replace BCM.

Important: Before performing a diagnostic procedure, you must always vehicle system diagnostic check.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Reference voltage for instrument cluster dimmer	Battery voltage above threshold	Battery voltage above threshold	Voltage above threshold	Battery voltage above threshold
Instrument Cluster Dimmer Control Circuit	B3600	B3600	1	B3600
1. Interior lighting does not work

1. Delete the trouble code. Disconnect the mirror control switch (lighting controller).
2. Connect a multimeter between the instrument cluster dimmer voltage reference circuit and the negative battery terminal.
3. Turn on the ignition, check the voltage level 9-14 V.
• If less than 9 volts, test the instrument cluster dimmer voltage reference circuit for a short to ground, an open, or high resistance. If there are no abnormal circuits or connections, replace the BCM.
• If greater than 14 volts, test the instrument cluster dimmer voltage reference circuit for a short to battery voltage. If there are no abnormal circuits or connections, replace the BCM.
4. If the voltage is correct and all circuits and connections are OK, replace the mirror control switch (lighting controller).

Important: Perform a Post-Repair Diagnostic Check at the end of each diagnostic procedure.

• Mirror control switch (lighting regulation), replacement
• Controller information for BCM replacement and programming.

• The voltage in the system is 9 - 16 V.
• The fault code can only be set when the output is activated.

• This DTC is set only when the output is activated and in the relay coil control circuit "work/start" there is a short to ground.

• The output driver of the controller will be disabled and the supply voltage will not be applied to the control circuit of the relay coil "work/start".

• The current fault code is cleared after the command is removed from the controller to exit or the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• Use the multimeter's MIN/MAX function to locate an intermittent fault.
• Short circuit to supply voltage in the control circuit of the relay winding "work/start" will cause the warning light to come on (MIL) with the ignition key in the OFF position.

1. Ignition OFF, disconnect the IGN MAIN PCB relay and connect a test lamp between the relay control circuit and ground.
2. Alternately turn the ignition on and off. The control lamp should light up and go out at change of position of the switch of ignition.
• If the test lamp never illuminates, test the relay control circuit for a short to ground, an open, or high resistance. If the circuit is OK, replace the BCM.
• If the test lamp stays on, test the relay control circuit for a short to battery voltage. If the circuit is OK, replace the BCM.
3. If the test lamp comes on and off normally, check or replace the IGN MAIN PCB relay.

• Ignition switch in the ACC or RUN position.
• The car was started remotely.
• Vehicle is in auxiliary power hold mode (RAP).

• The voltage in the system is 9 - 16 V.
• The fault code can only be set when the output is activated by command from the controller.

• This DTC is set only when the controller activates the output, and in the control circuit of the relay coil "Job" there is a short to ground.

• The controller's output driver will be disabled and no supply voltage will be applied to this circuit.

• The current fault code is cleared after the command is removed from the controller to exit or the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• Use the multimeter's MIN/MAX function to locate an intermittent fault.
• Short circuit to supply voltage in the control circuit of the relay winding "work/start" will cause the warning light to come on (MIL) with the ignition key in the OFF position.

1. Ignition OFF, disconnect the RUN relay and connect a test lamp between the relay control circuit "Job" and positive battery voltage. The control lamp should not light up.
• If the test lamp lights up, check the control circuit of the relay coil "Job" for a short to ground. If the circuits are OK and the DTC is in the status "current", replace BCM.
2. If the circuits are OK and the DTC is in the status "current", check or replace the RUN relay or BCM.

• Ignition switch is in the RUN position (JOB).

• The BCM detects an open or short to voltage in the voltage circuit "off/work/start", when both parameters "ignition auxiliary voltage/work" And "ignition work/start" active.
• The BCM detects an open in the battery positive voltage circuit while the engine is running. An open in the battery voltage circuit can be caused by a short to ground in one of the following circuits:
- Battery positive voltage - Auxiliary voltage - Ignition voltage 1 -Voltage "off/work/start"

• The controller enters the emergency power mode depending on the last detected active power mode and the status of the engine operation flag in the GMLAN serial communication circuits.
• The rest of the controllers on the vehicle operate in emergency power mode depending on the last valid power mode reported by the BCM and the status of the engine run flag on the GMLAN serial link circuits.
• The engine cannot be started.

• The current fault code is cleared after the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• Use the multimeter's MIN/MAX function to locate an intermittent fault.

1. Ignition OFF, disconnect the BCM connector.
2. Ignition OFF, key removed, and key in the ACC position, measure 0 V between the voltage circuit "off/work/start" at the BCM connector and ground.
• If the voltage is greater than 0V, disconnect the ignition switch and check the voltage circuit "off/work/start" for a short to voltage or a short to other ignition switch signal circuits.
3. Ignition OFF and key inserted, measure the battery voltage between the OFF/Run/Start voltage circuit" at the BCM connector and ground.
• If the voltage is lower than the battery voltage, disconnect the ignition switch and check the voltage circuit "off/work/start" for an open or short to ground.
4. With the ignition key in the RUN and START positions, measure the battery voltage between the voltage circuit "ignition 1" at the BCM connector and ground.
• If the voltage is lower than the battery voltage, disconnect the ignition switch and check the voltage circuit "ignition 1" and the battery positive voltage circuit for an open or short to ground.
5. With the ignition key in the ACC and RUN positions, measure the battery voltage between the auxiliary voltage circuit at the BCM connector and ground.
• If the voltage is lower than battery voltage, disconnect the ignition switch and test the ignition voltage circuit and battery positive voltage circuit for an open or short to ground.

• The ignition switch is in the START position.

• Chain "off/work/start" closed to supply voltage for more than 2 seconds.
• In chain "off/work/start" the break lasts longer than 2 seconds.

• The controller enters the emergency power mode depending on the last detected active power mode and the status of the engine operation flag in the GMLAN serial communication circuits.
• The rest of the controllers on the vehicle operate in emergency power mode depending on the last valid power mode reported by the BCM and the status of the engine run flag on the GMLAN serial link circuits.

• The current fault code is cleared after the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• Use the multimeter's MIN/MAX function to locate an intermittent fault.

1. With the key out of the ignition and in the ACC position, test for infinite resistance between the battery positive voltage and battery voltage terminals "off/work/start" on the ignition switch. Repeat the same measurement between the signal leads from the ignition key resistor and voltage "off/work/start" on the ignition switch.
• If the resistance is not infinite, replace the ignition switch.
2. With the ignition key in the OFF position, measure for less than 1 ohm between the battery positive voltage and battery voltage terminals "off/work/start" on the ignition switch.
• If resistance is greater than 1 ohm, replace the ignition switch.
3. With the ignition key in the RUN position, measure less than 1 ohm between the signal terminals from the ignition key resistor and the voltage "off/work/start" on the ignition switch.
• If resistance is greater than 1 ohm, replace the ignition switch.
4. With the key in the START position, measure the resistance of 1170-1430 ohms between the signal terminals from the ignition key resistor and voltage "off/work/start" on the ignition switch.
• If the measured value is not within the specified limits, replace the ignition switch.

• Ignition switch in the ACC or RUN position.
• The car was started remotely.
• Vehicle is in auxiliary power hold mode (RAP).

• The voltage in the system is 9 - 16 V.
• A fault code can only be issued when the output is activated by command from the controller.

• The DTC will only set when the controller activates the output and there is a short to ground in the RAP relay control circuit.

• The controller's output driver will be disabled and no supply voltage will be applied to this circuit.

• The current fault code is cleared after the command is removed from the controller to exit or the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• Use the multimeter's MIN/MAX function to locate an intermittent fault.
• The RAP radio mode is a standalone feature and continues to operate normally.
• The ignition switch will not return to the OFF position if the RAP relay is not energized.

1. Disconnect the RAP relay and connect a test lamp between the RAP relay control circuit and ground.
2. Turn on the ignition. The control lamp should light up.
• If the test lamp does not illuminate, test the relay control circuit for a short to ground. If the circuit is OK, replace the BCM.
• If the test lamp illuminates, check or replace the RAP relay.

• The battery voltage should be 9-16V.

• This fault code will be removed from the current ones after the cause of the fault has been eliminated.
• The DTC in the log will be cleared after 100 consecutive ignition cycles without the presence of a fault.
• The fault code in the log and the current code can be cleared with a scan tool.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Install the diagnostic tool. Turn on the ignition. Is DTC B1480 present?	-	Go to Step 3	Check for Intermittent Fault and Loose Connectors
3	Check the erroneously turned on power supply circuit of the entrance lighting for a short to ground. Has the cause been found and fixed?	-	Go to Step 5	Go to Step 4
4	Replace body controller (BCM). Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	Go to Step 5	-
5	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 2	System OK

DTC Descriptions

Battery voltage above threshold

Voltage above threshold

• Battery voltage drops below 11 V, engine speed is above 1100 rpm for 15 seconds.
• Battery voltage is above 16V, engine speed is above 1100 rpm for 15 seconds.
• The battery voltage differs by 2 V on the battery monitoring circuits in the BCM for 10 seconds.

• The fault code will lose current status after the fault disappears.
• After 50 consecutive ignition cycles, if there is no fault condition, the fault code is cleared from the log.
• To clear the DTC, use the scan tool function "Deleting trouble codes".

3. This step performs a voltage test on the battery positive voltage monitoring circuits in the BCM. If the voltage values are not within the specified range, check the voltage monitoring circuits.
4. This step tests the BCM ground circuit.
5. This step checks for proper voltage on the BCM ground circuits. If the voltage is not within the appropriate operating range, the battery positive voltage and BCM ground circuits need to be checked.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Install the diagnostic tool. Switch on the ignition with the engine off. Use a scan tool to monitor the Battery Voltage parameters in the BCM data list. Do any voltages differ by more than the specified value?	2 V	Go to Step 5	Go to Step 3
3	Switch off the ignition. Disconnect the BCM harness connectors. Switch on the ignition with the engine off. Measure the voltage between the BCM battery positive voltage circuits and the BCM ground circuits. Do the voltages differ by more than the specified value?	2 V	Go to Step 9	Go to Step 4
4	Measure the voltage between the battery positive voltage circuit at the BCM and a good ground. Do the voltages differ by more than the specified value?	2 V	Go to Step 8	Go to Step 7
5	Turn on the ignition. Measure the voltage between the battery positive voltage circuit and the ground circuit at the BCM. Is the measured value within the specified range?	10.5 - 15.5 V	Go to Step 9	Go to Step 6
6	Measure the voltage between the battery positive voltage circuit at the BCM and a good ground. Is the measured value within the specified range?	10.5 - 15.5 V	Go to Step 8	Go to Step 7
7	Test the battery positive voltage circuits at the BCM for high resistance or an open. Has the cause been found and fixed?	-	Go to Step 11	Go to Step 9
8	Test the ground circuits at the BCM for high resistance or an open. Has the cause been found and fixed?	-	Go to Step 11	Go to Step 9
9	Check for a poor connection at the body controller harness connector. Has the cause been found and fixed?	-	Go to Step 11	Go to Step 10
10	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	Go to Step 11	-
11	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 2	System OK

• The conditions for issuing this DTC are no longer valid.
• The fault code is removed from the log after 100 ignition cycles without a fault.
• The BCM is commanded to clear the code from the scan tool.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Front fog lamp control circuit	B2530	B2530	B2530	-

1. Ignition OFF, disconnect connector J2 on the instrument panel fuse box and test for a short to voltage, short to ground, open or high resistance at terminal 32.
2. Ignition ON, activate the scan tool fog lamp output control, and test the ground circuit at connector terminal 32 on the instrument panel fuse box.
• If ground is present, replace the engine fuse box. If ground is missing, replace the BCM.

• Dashboard Fuse Block Replacement
• Controller Information for BCM Replacement and Programming

• This fault code will be removed from the current ones after the cause of the fault has been eliminated.
• The DTC in the log will be cleared after 100 consecutive ignition cycles without the presence of a fault.
• DTCs in the log can be cleared with a scan tool.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Install the diagnostic tool. Switch on the ignition with the engine off. Using the scan tool, select the headlamp test and command the reversing lamps on and off. Do the reversing lights turn on and off according to commands?	-	Go to Diagnostic Tips	Go to Step 3
3	Check the reverse light power circuit for a short to ground or an open. Has the cause been found and fixed?	-	Go to Step 6	Go to Step 4
4	Check power circuit from CHMSL/BACKUP fuse (center stop/reverse) to the BCM for a short to ground or an open.	-	Go to Step 6	Go to Step 5
5	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	Go to Step 6	-
6	Use a scan tool to clear the DTCs. Operate the vehicle under the conditions that caused the DTC to occur. Is the DTC cleared?	-	Go to Step 2	System OK

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Headlamp Low Relay Control Circuit	B2575	B2575	B2575	-
Low Beam Relay Battery Supply Voltage Circuit	B2575	B2575	-	-

• A command was given to turn on the headlights.
• The headlight dimmer should be in the low beam position.

• The dipped beam relay control circuit has an open, short to ground, or short to voltage.
• There is an open or short to ground in the low beam relay battery supply voltage circuit.

• The conditions for issuing this DTC are no longer valid.
• The fault code is removed from the log after 100 ignition cycles without a fault.
• The BCM is commanded to clear the code from the scan tool.

1. Ignition OFF, disconnect connector J2 on the engine fuse box, and test connector terminal 26 for a short to voltage, short to ground, open, or high resistance.
2. Turn on the headlight switch, set the low/high beam switch to the low position, and test the terminal 26 circuit at J2 for ground.
• If ground is present, replace the engine fuse box. If ground is missing, replace the BCM.

Important: Before performing a diagnostic procedure, you must always vehicle system diagnostic check.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Headlight switch off	B257A	B257A	B257A	-
Parking light switch on	B257A	B257A	B257A	-
Headlight switch on	1	2	B2575	-
headlight weight	-	B257A	2	-
Headlights are constantly on - low beam or high beam Headlights do not work - low beam

1. Set the headlight switch to the OFF position, disconnect the J6 connector of the BCM.
2. Ignition ON, connect a test lamp between the headlight switch OFF circuit and the positive battery terminal. Make sure the control lamp is on.
• If the control lamp does not light up:
Test the headlight switch OFF circuit for a short to voltage or an open.
Check headlight ground circuit.
If the circuit/connections are OK, replace the headlight switch.
6. Set the headlight switch to the PARK position. Verify that the control lamp is off.
• If the test lamp illuminates, test the headlight switch OFF circuit for a short to ground. If the circuit/connections are OK, replace the headlight switch.
7. Set the headlight switch to the PARK position. Connect a test lamp between the park light switch ON circuit and the positive battery terminal. Make sure the control lamp is on.
• If the test lamp does not illuminate, test the parking light switch ON circuit for a short to voltage or an open. If the circuit/connections are OK, replace the headlight switch.
8. Set the headlight switch to the OFF position. Verify that the control lamp is off.
• If the test lamp illuminates, test the parking light switch ON circuit for a short to ground. If the circuit/connections are OK, replace the headlight switch.
9. If there are no abnormal circuits or connections, replace the BCM.

Important: Perform a Post-Repair Diagnostic Check at the end of each diagnostic procedure.

• Headlight switch replacement
• Controller Information for BCM Replacement and Programming

• When the BCM is commanded to OFF high beams and the high beam relay control circuit is shorted to ground.
• When the BCM is commanded to turn ON high beams and the high beam relay control circuit is shorted to voltage or open.

• This fault code will be removed from the current ones after the cause of the fault has been eliminated.
• The DTC in the log will be cleared after 100 consecutive ignition cycles without the presence of a fault.
• The fault code in the log and the current code can be cleared with a scan tool.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Install the diagnostic tool. Switch on the ignition with the engine off. Using a scan tool, command the high beam relay on and off. Does the high beam relay turn on and off according to received commands?	-	Check for Intermittent Fault and Loose Connectors	Go to Step 3
3	Switch off the ignition. Disconnect the high beam relay. Switch on the ignition with the engine off. Test the high beam relay positive voltage circuit with a test lamp connected to a good ground. Does the control lamp light up?	-	Go to Step 4	Go to Step 10
4	Connect a test lamp between the high beam relay control circuit and the high beam relay battery positive voltage circuit. Using a scan tool, command the high beam relay on and off. Does the control lamp turn on and off according to each command?	-	Go to Step 8	Go to Step 5
5	Does the control lamp stay on with any command?	-	Go to Step 7	Go to Step 6
6	Test the high beam relay control circuit for a short to battery positive voltage or an open. Has the cause been found and fixed?	-	Go to Step 14	Go to Step 9
7	Test the high beam relay control circuit for a short to ground. Has the cause been found and fixed?	-	Go to Step 14	Go to Step 9
8	Test the high beam relay in the engine fuse box for high resistance or poor contact. Has the cause been found and fixed?	-	Go to Step 14	Go to Step 12
9	Check for high resistance or poor contact at the body controller harness connector (BCM). Has the cause been found and fixed?	-	Go to Step 14	Go to Step 13
10	Check the harness connectors at the engine fuse box for high resistance or poor contact. Has the cause been found and fixed?	-	Go to Step 14	Go to Step 11
11	Replace engine fuse block. Has the repair been completed?	-	Go to Step 14	-
12	Replace the high beam relay in the engine fuse box. Has the repair been completed?	-	Go to Step 14	-
13	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	Go to Step 14	-
14	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 2	System OK

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Parking light relay control	B2585	B2585	B2585	-

• The conditions for issuing this DTC are no longer valid.
• The fault code is removed from the log after 100 ignition cycles without a fault.
• The BCM is commanded to clear the code from the scan tool.

1. Ignition OFF, disconnect connector J2 on the engine fuse box, and test connector terminal 33 for a short to voltage, short to ground, an open, or high resistance.
2. Using the scan tool, activate parking light output control and test ground at terminal 33 of connector J2 on the engine fuse box.
• If ground is present, replace the engine fuse box. If ground is missing, replace the BCM.

• Engine Fuse Block Replacement
• Controller Information for BCM Replacement and Programming

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Power supply of the LED indicator light regulator	B2625	B2625	B2625	-

• The conditions for issuing this DTC are no longer valid.
• The fault code is removed from the log after 100 ignition cycles without a fault.
• The BCM is commanded to clear the code from the scan tool.

1. Turn off the ignition, turn off the parking lights, disconnect all the elements of the LED indicator in the power circuit of the dimmer. Verify DTC B2625 is not set.
• If the DTC resets, test the LED dimmer supply voltage circuit for a short to voltage, a short to ground, or an open. If the circuit/connections are OK, replace the BCM, driver's door switch, and passenger's door switch, respectively.
2. Connect the elements one at a time and check for the issuance of a fault code B2625.
• If the DTC resets, replace the appropriate item.
• If no DTC is set, replace the BCM.

• Refer to the appropriate procedure for replacing the component causing the problem.
• Controller Information for BCM Replacement, Tuning and Programming

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Ambient light sensor signal circuit	B2645 Ambient light sensor circuit above threshold	B2645 Ambient Light Sensor Circuit Below Threshold	B2645 Ambient light sensor circuit above threshold	B2645 Ambient light sensor circuit below threshold or B2645 Ambient light sensor circuit above threshold
Ambient light sensor ground circuit	-	B2645 Ambient Light Sensor Circuit Below Threshold	-	B2645 Ambient light sensor circuit below threshold or B2645 Ambient light sensor circuit above threshold

• The cause of this DTC has been corrected.
• A scan tool command was issued to clear DTCs.
• The fault code in the log is cleared after 100 consecutive ignition cycles without a fault.

1. Switch off the ignition, disconnect the ambient light sensor.
2. Turn on the ignition, observe the parameter "Ambient light sensor" in the BCM data list on the scan tool.
• If the scan tool parameter reads less than 7 V, troubleshoot and repair an open, high resistance, or short to ground in the ambient light sensor signal circuit, or replace the ambient light sensor.
• If the scan tool parameter is greater than 10.5 V, locate and repair a short to voltage in the ambient light sensor signal circuit.
3. If the circuits are OK, replace the BCM.

• Replacing the ambient light sensor
• Controller Information for BCM Replacement and Programming

1. The ignition switch is in the ON position.
2. The brake pedal is pressed.
3. Transmission in PARK position.

• The current DTC B2705 will clear when the fault clears and the ignition is turned off and on.
• All BCM DTCs in the log will clear after 100 ignition cycles with no current DTCs generated for 100 ignition cycles.

1. Verify that there are no DTCs associated with the brake pedal position sensor and/or transmission internal mode switch using a scan tool (IMS), which may prevent the BCM from applying battery voltage to the BTSI solenoid.
2. If the automatic transmission shift interlock control circuit is shorted to battery positive voltage, the BTSI solenoid will not operate. Vehicles with a floor-mounted shift lever will shift from PARK without depressing the brake pedal. On vehicles with a steering column gear selector, the selector lever must be locked in the PARK position.
3. Perform checks by shaking wires and connectors. Thus, intermittent faults can often appear.

2. Listen for a click when the BTSI solenoid fires. Issue a command to turn on and off. Repeat commands if necessary.
3. This step tests the battery voltage in the BTSI solenoid control circuit.
4. At this point, the BTSI solenoid control circuit is tested for an open or short to ground.
5. This step tests for an open ground circuit on the BTSI solenoid.

Step	Operation	Values	Yes	No
1	Install the diagnostic tool. Switch on the ignition with the engine off. Using a scan tool, command the lockout solenoid on and off. Using a scan tool, check the BTSI solenoid control parameter in the body controller data sheet (BCM). Does the BTSI solenoid turn on and off according to commands?	-	Check for intermittent faults and loose connectors.	Go to Step 2
2	Switch off the ignition. Disconnect the BTSI solenoid. Connect a test lamp between the BTSI solenoid control circuit at the BTSI solenoid connector and a good ground. Switch on the ignition with the engine off. Using a scan tool, command the BTSI solenoid on and off several times. Does the control lamp light up and go out in accordance with the commands?	-	Go to Step 4	Go to Step 3
3	Test the BTSI solenoid control circuit for an open or short to ground. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 6
4	Test the ground circuit of the BTSI solenoid for an open. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 5
5	Inspect the harness connector on the BTSI solenoid for poor connections. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 7
6	Check for a poor connection at the body controller harness connector. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 8
7	Replace BTSI solenoid. Has the replacement been completed?	-	Go to Step 9	-
8	Important: Follow the BCM controller setup procedures. Replace BCM. Has the replacement been completed?	-	Go to Step 9	-
9	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 1	System OK

• The EBCM disables the ABS-TCS/ESP systems during the ignition cycle.
• One or more of the following warning indicators may be on:
• ABS-TCS warning indicator,
• Warning indication ABS-TCS,
• ESP warning indication,
• Brake fault indicator and/or
• Off course warning indication.

2. Confirmation that the fault that caused this DTC is currently present.
3. Confirmation of the integrity of the internal circuits of the ECBM controller. An internal fault within the ECBM may cause this DTC to be set.

Step	Operation	Values	Yes	No
1	Is the diagnostic system check complete?	-	Go to Step 2	Go to Diagnose Schema Check in this section.
2	Switch off the ignition for 10 seconds. Operate the vehicle under the condition that caused this DTC to set or road test it at speeds greater than 15 km/h. View DTCs with a scan tool. Whether DTC C0131 is set (B2745) in this ignition cycle?	-	Go to Step 3	Go to Step 4
3	Are DTCs C0550 or C0551 also set?	-	Refer to DTCs C0550 and C0551 in this section.	Go to Step 4
4	Test all ground circuits of the EBCM for high resistance or an open. Check ABS-TCS/ESP fuses and replace if necessary. Test the EBCM battery voltage circuit for high resistance, an open, or short to ground. Has any cause of the problem been found and corrected?	-	Go to Step 7	Go to Step 5
5	Check the EBCM wiring connector for loose connections. Has any cause of the problem been found and corrected?	-	Go to Step 7	Go to Step 6
6	Replace hydraulic modulator. Cm. "Brake modulator assembly" in this section. Is the repair finished?	-	Go to Step 7	-
7	Clear DTCs using a scan tool. Switch off the ignition for 10 seconds. Test the vehicle under the conditions that led to DTC C0131 (B2745). Whether DTC C0131 is set (B2745) in this ignition cycle?	-	Go to Step 2	Go to Step 8
8	On the scan tool, select the DTC display function. Does the scan tool display any DTCs?	-	Go to the appropriate DTC table.	System OK

Important: Before performing a diagnostic procedure, you must always vehicle system diagnostic check.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Horn relay control	1	2	B2750	-
Sound control	2	2	2	-
Ground horn	-	2	-	-
Horn switch ground	-	2	-	-
Horns are constantly on Horn devices do not work

• The fault code is cleared after the fault disappears.
• The current fault code will be logged when the exit request is cleared.
• The fault code in the log will be cleared after 50 consecutive ignition cycles without a fault.

1. Ignition OFF, disconnect the J2 harness connector at the engine fuse box.
2. Connect a test lamp between the control circuit at terminal 22 and battery voltage.
3. Use the scan tool to command the horn on and off. The control lamp should light up and go out in accordance with the commands.
• If the test lamp stays on, test the control circuit for a short to ground. If the circuit is OK, replace the body controller.
• If the test lamp stays off, test the control circuit for a short to voltage or an open/high resistance. If the circuit is OK, replace the body controller.
4. If all circuits test normal, check or replace the engine fuse block.

Important: Perform a Post-Repair Diagnostic Check at the end of each diagnostic procedure.

• Junction block replacement
• Controller Information for Body Controller Replacement and Programming

• The voltage in the system should be 9-16 V.
• The anti-theft system is in a ready state.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Switch off the ignition. Disconnect the tilt sensor harness connector. Test the battery positive voltage circuit at the tilt sensor harness connector with a test light connected to a good ground. Does the control lamp light up?	-	Go to Step 3	Go to Step 7
3	Using a DMM, measure the voltage on the tilt sensor signal circuit at the tilt sensor harness connector. Is the measured voltage equal to the battery voltage?	9 - 16 V	Go to Step 4	Go to Step 5
4	Test the tilt sensor power circuit for a short to battery voltage, a short to ground, or an open circuit. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 6
5	Test the tilt sensor signal circuit for an open or short to ground. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 6
6	Check for a loose or loose connection in the tilt sensor harness connector. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 8
7	Repair the tilt sensor battery positive voltage supply circuit. Has the cause been removed?	-	Go to Step 9	-
8	Replace tilt sensor. Has the cause been removed?	-	Go to Step 9	-
9	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 10	System OK
10	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	System OK	-

• The voltage in the system should be 9-16 V.
• The anti-theft system is in a ready state.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Switch off the ignition. Disconnect the intrusion sensor harness connector. Test the battery positive voltage circuit at the intrusion sensor harness connector with a test light connected to a good ground. Does the control lamp light up?	-	Go to Step 3	Go to Step 7
3	Using a DMM, measure the voltage on the intrusion sensor signal circuit at the intrusion sensor harness connector. Is the measured voltage equal to the battery voltage?	9 - 16 V	Go to Step 4	Go to Step 5
4	Test the intrusion sensor power circuit for a short to battery voltage, a short to ground, or an open circuit. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 6
5	Test the faulty tilt sensor signal circuit for an open or short to ground. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 6
6	Check for a loose or loose connection in the intrusion sensor harness connector. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 8
7	Repair the battery positive voltage supply circuit to the intrusion sensor. Has the cause been removed?	-	Go to Step 9	-
8	Replace intrusion sensor. Has the replacement been completed?	-	Go to Step 9	-
9	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 10	System OK
10	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	System OK	-

Important: Before performing a diagnostic procedure, you must always vehicle system diagnostic check.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Passenger door release relay control	B3130	1	1	-
Power door locks not working - all doors

1. Disconnect connector J2 on the instrument panel fuse box. Check if the DTC is reset.
• If the DTC does not reset, replace the instrument panel fuse box.
2. Check the door power relay control circuit for a short to voltage.
• If all circuits and connections are normal, replace the BCM.

Important: Perform a Post-Repair Diagnostic Check at the end of each diagnostic procedure.

• Controller Information for BCM Replacement, Tuning and Programming
• Dashboard Fuse Block Replacement

Important: Before performing a diagnostic procedure, you must always vehicle system diagnostic check.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Door Lock Relay Control	B3135	1	1	-
Power door locks not working - all doors

1. Disconnect the lock relay in the instrument panel fuse box. Check if the DTC is reset.
• If no DTC is set, replace the relay.
2. Disconnect connector J2 on the instrument panel fuse box. Check if the DTC is reset.
• If the DTC does not reset, replace the instrument panel fuse box.
3. Test the door lock relay control circuit for a short to ground.
• If all circuits and connections are normal, replace the BCM.

Important: Perform a Post-Repair Diagnostic Check at the end of each diagnostic procedure.

• Controller Information for BCM Replacement, Tuning and Programming
• Dashboard Fuse Block Replacement

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Lift window release switch signal	1	1	1	-
Lifting glass latch release signal	B3265	1	1	-
Lift window release control	1	1	1	-
Lift-window release switch ground	-	1	-	-
Lift window release weight	-	1	-	-
Lift glass latch release does not work

• The voltage in the system should be 9-18 V.
• An attempt is made to unlock the lifting window.

• The DTC is current only as long as the liftgate command is active.
• The fault code in the log will clear after 50 ignition cycles without a fault.

1. Disconnect the BCM connector J3.
2. Verify that the test lamp does not illuminate when connected between the battery voltage circuit and the lift glass latch release signal circuit terminal at the harness connector.
• If the test lamp illuminates, test the signal circuit for a short to ground. If the circuits are OK, replace the rear wiper motor controller.
3. If the liftgate latch release signal circuit is OK, replace the BCM.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Stop lamp supply voltage	B3445	B3445	B3445	-

• The conditions for issuing this DTC are no longer valid.
• The fault code is removed from the log after 100 ignition cycles without a fault.
• The BCM is commanded to clear the code from the scan tool.

1. Disconnect the brake lights and test each brake light assembly individually for internal shorts between all terminals.
• If shorts are found between the terminals, replace the brake light socket or board, respectively.
2. Test the stop lamp power circuit for a short to voltage, a short to ground, an open, or high resistance.
• If all circuits and connections are normal, replace the BCM.

• Replacing the rear light bulb
• Controller Information for BCM Replacement and Programming

Important: Before performing a diagnostic procedure, you must always vehicle system diagnostic check.

• The DTC setting condition is corrected and the DTC is cleared with a scan tool.
• The BCM automatically clears the DTC in the log if the current DTC is not detected within 100 consecutive ignition cycles.

• This DTC can only set when the output is activated by command from the BCM.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to Vehicle Diagnostic System Check
2	Switch off the ignition. Disconnect the intrusion sensor harness connector. Disconnect the BCM harness connector. Test the rain sensor auxiliary voltage circuit for a short to ground or an open. Has the cause been found and fixed?	-	Go to Step 7	Go to Step 3
3	Test the rain sensor ground circuit for an open or short to voltage. Has the cause been found and fixed?	9 - 16 V	Go to Step 7	Go to Step 4
4	Test the rain sensor signal circuit 2 for an open or short to ground, or a short to voltage. Has the cause been found and fixed?	-	Go to Step 7	Go to Step 5
5	Check for a loose or loose connection at the rain sensor harness connector. Has the cause been found and fixed?	-	Go to Step 7	Go to Step 6
6	Replace rain sensor. Has the cause been removed?	-	Go to Step 7	-
7	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 8	System OK
8	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	System OK	-

• This DTC can only set when the output is activated by command from the BCM.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to Vehicle Diagnostic System Check
2	Switch off the ignition. Disconnect the intrusion sensor harness connector. Disconnect the BCM harness connector. Test the rain sensor auxiliary voltage circuit for a short to ground or an open. Has the cause been found and fixed?	-	Go to Step 7	Go to Step 3
3	Test the rain sensor ground circuit for an open or short to voltage. Has the cause been found and fixed?	9 - 16 V	Go to Step 7	Go to Step 4
4	Test the rain sensor signal circuit 1 for an open or short to ground, or a short to voltage. Has the cause been found and fixed?	-	Go to Step 7	Go to Step 5
5	Check for a loose or loose connection at the rain sensor harness connector. Has the cause been found and fixed?	-	Go to Step 7	Go to Step 6
6	Replace rain sensor. Has the replacement been completed?	-	Go to Step 7	-
7	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 8	System OK
8	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	System OK	-

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Windshield washer switch signal	6	8	1	-
Windshield wiper motor relay coil supply voltage	B3715	2	6	-
Windshield wiper high speed switch signal	6	4	1	-
Windshield wiper low speed switch signal	B3922	3	1	-
Windshield wiper motor park switch signal	5	5	-	-
High speed windshield wiper motor control	2	4	-	-
Windshield Wiper Motor Low Speed Control	2	3	-	-
Windshield wiper motor weight	-	2	-	-
Windshield wiper switch ground	-	1	-	-
Wiper high speed relay control	7	4	B3875	-
Ground wiper relay	-	2	-	-
Windshield wipers and washers do not work in any mode. The windshield wipers do not work in any mode, but the windshield washers work. The delay or low speed wipers do not work. The high speed windshield wipers do not work. Wiper parking not working. Windshield wipers are constantly working. Wipers in low speed mode operate at high speed. Violation of the glass washer.

• The current DTC goes into the log when the exit command is canceled or the cause of the DTC is removed.
• The DTC in the log will be cleared after 50 consecutive ignition cycles without the presence of a fault.

1. Ignition OFF, disconnect the J2 harness connector at the engine fuse box.
2. Connect a test lamp between the control circuit at terminal 25 and ground.
3. Use the scan tool to command the wiper relay on and off. The control lamp should light up and go out in accordance with the commands.
• If the test lamp stays on, test the control circuit for a short to voltage. If the circuits are OK, check or replace the body controller.
• If the test lamp never illuminates, test the control circuit for a short to ground, an open, or high resistance. If the circuits are OK, check or replace the body controller.
4. If all circuits test normal, check or replace the engine fuse block.

Important: Perform a Post-Repair Diagnostic Check at the end of each diagnostic procedure.

• Engine Fuse Block Replacement
• Controller Information for BCM Replacement and Programming

DTC Descriptions

Wrong signal

stuck drive

• The speed stabilizer switch is set to the on position.
• The ignition switch is set to the ON position.

• The BCM detects an incorrect voltage signal on the switch signal circuits "+ RES" And "- SET" speed control systems.
• The condition described is valid for 0.5 seconds.

• The BCM stores the DTC information in memory if the diagnostic run ends with a fault detected.
• Malfunction indicator lamp (MIL) does not burn.
• The cruise control system is disabled.

• The fault code is transferred to the log after the fault has been corrected.
• The fault code in the log is cleared after 100 ignition cycles without a fault.
• The BCM is commanded to clear the code from the scan tool.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Install the diagnostic tool. Switch on the ignition with the engine off. Using a scan tool, observe the Cruise Control Switch parameter. Parameter "cruise control switch" shows an error?	-	Go to Step 3	Go to Step 4
3	Switch off the ignition. Disconnect the Multi-ASM switch. Switch on the ignition with the engine off. Using a scan tool, observe the Cruise Control Switch parameter. Parameter "cruise control switch" shows an error?	-	Go to Step 9	Go to Step 11
4	Set the speed stabilizer switch to the on position. Using a scan tool, observe the Cruise Control Switch parameter. Parameter "cruise control switch" shows an error?	-	Go to Step 7	Go to Step 5
5	Push the switch "SET/COAST"automatic speed control systems. Using a scan tool, observe the parameter "cruise control switch". Parameter "cruise control switch" shows an error?	-	Go to Step 7	Go to Step 6
6	Push the switch "RESUME/ACCEL"automatic speed control systems. Using a scan tool, observe the parameter "cruise control switch". Parameter "cruise control switch" shows an error?	-	Go to Step 7	Go to Diagnostic Tips
7	Important: The cruise control switch must be in the ON position for the multimeter to correctly display the switch resistance values "SET/COAST". Switch off the ignition. Using a multimeter, measure the resistance at the cruise control switch between the voltage circuit "ignition 1" and switch signal circuit "SET/COAST" And "RESUME/ACCELERATE". Press and hold the cruise control function switches individually while measuring the resistance value of each cruise control function switch. Are the cruise control function switch resistance values measured within the specified ranges?	Off = open circuit On = 7.8 kΩ - 8.6 kΩ Resume = 2.7 kΩ - 3.0 kΩ Set = 1.2 kΩ - 1.3 kΩ	Go to Step 8	Go to Step 11
8	Check voltage circuit "ignition 1" for increased resistance. Has the cause been found and fixed?	-	Go to Step 15	Go to Step 10
9	Check switch signal circuits "SET/COAST" And "RESUME/ACCELERATE" cruise control systems for a short circuit to the supply voltage. Has the cause been found and fixed?	-	Go to Step 15	Go to Step 2
10	Check switch signal circuits "SET/COAST" And "RESUME/ACCELERATE" cruise control systems for increased resistance. Has the repair been completed?	-	Go to Step 15	Go to Step 12
11	Inspect the Multi-ASM switch for poor contact. Has the cause been found and fixed?	-	Go to Step 15	Go to Step 13
12	Check for a poor connection at the body controller harness connector. Has the cause been found and fixed?	-	Go to Step 15	-
13	Replace cruise control switch. Has the replacement been completed?	-	Go to Step 15	-
14	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	Go to Step 15	-
15	Use a scan tool to clear the DTCs. Operate the vehicle under the conditions that caused the DTC to occur. Is the DTC cleared?	-	Go to Step 2	System OK

• The voltage in the system should be 9-16 V.
• The anti-theft system is in a ready state.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Check for a loose or loose connection in the intrusion sensor harness connector. Has the cause been found and fixed?	-	Go to Step 6	Go to Step 3
3	Check for a loose or loose connection at the body controller harness connector. Has the cause been found and fixed?	9 - 16 V	Go to Step 6	Go to Step 4
4	Switch off the ignition. Disconnect the intrusion sensor harness connector. Disconnect the BCM harness connector. Check the intrusion sensor ground circuit for an open. Has the cause been found and fixed?	-	Go to Step 6	Go to Step 5
5	Replace intrusion sensor. Has the replacement been completed?	-	Go to Step 6	-
6	Use a scan tool to clear the DTCs. Operate the vehicle under the DTC conditions listed in the accompanying text. Is the DTC cleared?	-	Go to Step 7	System OK
7	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	System OK	-

Important: Before performing a diagnostic procedure, you must always vehicle system diagnostic check.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Windshield washer switch signal	2	1	3	-
Windshield washer pump control	1	1	2	-
Windshield washer relay control	2	1	B3873	-
Windshield washer pump weight	-	1	-	-
Windshield wiper switch ground	-	3	-	-
Washer not working Washers on all the time Windshield Wiper System Malfunction

• The current DTC goes into the log when the exit command is canceled or the cause of the DTC is removed.
• The DTC in the log will be cleared after 50 consecutive ignition cycles without the presence of a fault.

1. Ignition OFF, disconnect the J2 harness connector at the instrument panel fuse box.
2. Connect a test lamp between the control circuit at terminal 43 and battery voltage.
3. Use the scan tool to command the wiper/washer motor on and off. The control lamp should light up and go out in accordance with the commands.
• If the test lamp stays on, test the control circuit for a short to ground. If the circuit is OK, replace the body controller.
• If the test lamp stays off, test the control circuit for a short to voltage or an open/high resistance. If the circuit is OK, replace the body controller.

5. If all circuits test normal, check or replace the engine fuse block.

Important: Perform a Post-Repair Diagnostic Check at the end of each diagnostic procedure.

• Junction block replacement
• Controller Information for BCM Replacement and Programming

Important: Before performing a diagnostic procedure, you must always vehicle system diagnostic check.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Windshield washer switch signal	6	8	1	-
Windshield wiper motor relay coil supply voltage	B3715	2	6	-
Windshield wiper high speed switch signal	6	4	1	-
Windshield wiper low speed switch signal	B3922	3	1	-
Windshield wiper motor park switch signal	5	5	-	-
High speed windshield wiper motor control	2	4	-	-
Windshield Wiper Motor Low Speed Control	2	3	-	-
Windshield wiper motor weight	-	2	-	-
Windshield wiper switch ground	-	1	-	-
Wiper high speed relay control	7	4	B3875	-
Ground wiper relay	-	2	-	-
Windshield wipers and washers do not work in all modes Windshield wipers do not work in all modes, washers work Windshield wipers do not work in delay or low speed mode Windshield wipers not working at high speed Windshield wipers do not reset Windshield wipers always on Windshield wipers operate at high speed in low speed mode Washer malfunction

• The current DTC goes into the log when the exit command is canceled or the cause of the DTC is removed.
• The DTC in the log will be cleared after 50 consecutive ignition cycles without the presence of a fault.

1. Ignition OFF, disconnect the J2 harness connector at the engine fuse box.
2. Connect a test lamp between the control circuit at terminal 21 and battery voltage.
3. Use the scan tool to command the wiper high speed relay on and off. The control lamp should light up and go out in accordance with the commands.
• If the test lamp stays on, test the control circuit for a short to ground. If the circuits are OK, check or replace the body controller.
• If the test lamp stays off, test the control circuit for a short to voltage or an open/high resistance. If the circuits are OK, check or replace the body controller.
4. If all circuits test normal, check or replace the engine fuse block.

Important: Perform a Post-Repair Diagnostic Check at the end of each diagnostic procedure.

• Engine Fuse Block Replacement
• Controller Information for BCM Replacement and Programming

• The ignition switch is set to the ON position.
• The ignition voltage is between 9 and 16 V.

• The BCM does not activate the low speed output.
• The windshield wipers will only operate in high speed mode.

• This DTC clears when the cause of the problem is corrected.
• The history DTC will clear after 50 consecutive ignition cycles without a malfunction.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Set the ignition switch to the ON position (included). Turn the windshield wiper switch to all positions. Are the windshield wipers working properly?	-	Check for Intermittent Fault and Loose Connectors	Go to Step 3
3	Set the ignition switch to the OFF position. Disconnect the wiper switch connector. Using a scan tool, observe the parameter "Windscreen wiper switch". Switch on the ignition with the engine off. Does the parameter show "Windscreen wiper switch" state OFF (turned off)?	-	Go to Step 5	Go to Step 4
4	Test the low speed wiper switch signal circuit for the following: Short circuit to ground Short circuit to battery voltage Has the cause been found and fixed?	-	Go to Step 9	Go to Step 6
5	Inspect the harness connector at the windshield washer/wiper switch for loose connections. Has the cause been found and fixed?	-	Go to Step 9	Go to Step 7
6	Check for a poor connection in the body controller wiring harness connector (BCM). Has the cause been found and fixed?	-	Go to Step 9	Go to Step 8
7	Replace the windshield wiper switch. Cm. "Replacing the multifunction turn signal switch". Has the replacement been completed?	-	Go to Step 9	-
8	Replace BCM. Refer to the controller manual for replacement and programming procedures. Has the replacement been completed?	-	Go to Step 9	-
9	Clear the DTCs using a scan tool. Is the DTC cleared?	-	Go to Step 2	System OK

• The ignition is on.

• Segment lights up on HVAC controller "A/C OFF" ("air conditioning off").
• The air conditioner compressor turns off.

• The fault code will be logged if the HVAC controller stops detecting a fault.
• The fault code in the log will clear after 50 ignition cycles without a fault.
• The DTC can be cleared with a scan tool.

3. This step tests the correct operation of the circuit in the upper voltage range.
4. This step tests the circuit for proper operation in the lower voltage range. If the jumper fuse blows during this test, there is a short to voltage in the signal circuit.

Step	Operation	Values	Yes	No
1	Has the vehicle system diagnostic check been completed?	-	Go to Step 2	Go to section Vehicle system diagnostic check
2	Install the diagnostic tool. Switch on the ignition with the engine off. Using a scan tool, monitor the Evaporator Temp parameter. Does the scan tool indicate that the parameter "Evaporator temperature" is in the specified range?	0.09 - 4.90 V	Go to Step 3	Go to Step 4
3	Check the connection on the climate control panel and replace the leads if necessary. Is the repair finished?	-	System OK	Go to Step 4
4	Switch off the ignition. Disconnect the evaporator temperature sensor. Switch on the ignition with the engine off. Using a scan tool, monitor the Evaporator Temp parameter. Parameter "Evaporator temperature" above the specified value?	4.09 V	Go to Step 5	Go to Step 6
5	Switch off the ignition. Connect a jumper wire with a 3 amp fuse between the evaporator temperature sensor signal circuit and the low reference circuit of the evaporator temperature sensor. Switch on the ignition with the engine off. Using a scan tool, monitor the Evaporator Temp parameter. Parameter "Evaporator temperature" below the specified value?	0.09 V	Go to Step 10	Go to Step 7
6	Test the evaporator temperature sensor signal circuit for a short to ground. Has the cause been found and fixed?	-	Go to Step 14	Go to Step 11
7	Test the evaporator temperature sensor signal circuit for one of the following: Short circuit to supply voltage high resistance cliff Has the cause been found and fixed?	-	Go to Step 14	Go to Step 8
8	Test the evaporator temperature sensor low reference circuit for one of the following: high resistance cliff Has the cause been found and fixed?	-	Go to Step 14	Go to Step 9
9	Test the following signal circuits for a short to voltage: Cabin air temperature sensor Outdoor temperature sensor Left Sunlight Sensor Right Sunlight Sensor Ambient light sensor Has the cause been found and fixed? Has the cause been found and fixed?	-	Go to Step 14	Go to Step 11
10	Inspect the evaporator temperature sensor harness connector for loose connections. Has the cause been found and fixed?	-	Go to Step 14	Go to Step 12
11	Check harness connector at HVAC controller (HVAC) for contact violations. Has the cause been found and fixed?	-	Go to Step 14	Go to Step 13
12	Replace evaporator temperature sensor. See Section 7B, Manual control of the heating, ventilation and air conditioning system. Has the cause been found and fixed?	-	Go to Step 14	-
13	Replace HVAC controller. For replacement, setup, and programming procedures, see section 7B, "Manual control of the heating, ventilation and air conditioning system». Has the replacement been completed?	-	Go to Step 14	-
14	Use a scan tool to clear the DTCs. Operate the vehicle under the conditions that caused the DTC to occur. Is the DTC cleared?	-	Go to Step 2	System OK

• Wiring harness between up/down switch and BCM
• Gear up/down switch
• BCM

Gear lever position	output pin (6)
D	-0.3... 0.3 V
m	0.68... 0.78 V
M+	2.18... 2.55 V
M-	1.11... 1.30 V

Step	Operation	Values	Yes	No
1	Set the ignition switch to the OFF position. Connect the diagnostic tool. With the engine off, turn the ignition switch to the ON position. Select item "Saving status records/fault logs" on the menu "Information about diagnostic codes" Save status records/fault logs. Select item "Clear DTC Information" on the menu "Information about diagnostic trouble codes". Delete information about fault codes. Complete one cycle of driving. Is the winter mode light flashing?	-	Go to Step 2	Repair a temporary loose contact in the connector.
2	Select item "Request trouble codes by condition" on the menu "Information about diagnostic trouble codes". Request trouble codes by condition. Is DTC P0826 displayed?	-	Go to Step 3	Repair a temporary loose contact in the connector.
3	Test the 12V reference circuit for a short to ground or an open between the up/down switch and the BCM. Has a fault been found?	-	Repair short to ground or open circuit.	Go to Step 4
4	Test the signal circuit for an open, short to voltage, short to ground between the up/down switch and the BCM. Has a fault been found?	-	Repair an open, short to voltage, or ground in the signal circuit.	Go to Step 5
5	Inspect the circuit for an open, short to voltage, or ground between the up/down switch and ground. Has a problem been found?	-	Repair an open, short to voltage, or ground in the circuit.	Go to Step 6
6	With the ignition on, check the voltage at the output terminal of the up/down switch by moving the shift lever. See diagnostic guidelines. Does the measured value match the specified value?	-	Replace BCM.	Replace shift lever assembly.

• The supply voltage of the controllers is within the normal operating range.
• Vehicle power mode requires serial communication.

• The controller stops transmitting all commands.
• The controller uses standard values for all parameters received via serial communication lines.
• The controller inhibits the setting of all other DTCs.

• The current fault code is cleared after the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• The cause of the intermittent failure may be caused by a short in the high speed GMLAN links.
• This DTC cannot be received with current status. Symptom diagnostics in progress "The scan tool does not communicate with a device on a high speed GMLAN".
• Specific controllers using the high speed GMLAN link are listed in the link list.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Low speed GMLAN serial link	1	U0140 - U0214	1	-
Battery positive voltage circuits	U0100 - U0214	U0100 - U0214	-	-
Ignition Voltage Circuits	U0100 - U0214	U0100 - U0214	-	-
Controller Ground Circuits	-	U0100 - U0214	-	-
Auxiliary serial line wakeup circuit	U1814	U0100, U0101	-	-
Enable Serial Link	U2099	U0121	-	-
The scan tool does not communicate with a device on a high speed GMLAN

• The voltage in the system is 9 - 16 V.
• Serial communication is required for the vehicle power mode master to operate.

• The current fault code is cleared after the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• Using the above list of DTC definitions, determine which of the controllers is out of communication.
• If communication with multiple controllers is lost, select the one closest to the data link connector (DLC).
• For information about which GMLAN link - high speed or low speed - a particular controller uses, see "Reference information on communication channels".
• Some controllers lack internal protection for certain voltage outputs and may cause the battery positive voltage fuse or ignition voltage source to blow. If the input voltage fuse is blown but no short circuit is detected on this circuit, verify that the controllers do not have a voltage output circuit shorted to ground before replacing the controller.
• This diagnostic can be applied to any controller that needs to communicate over a high or low speed GMLAN serial link, provided the vehicle is equipped with the option that uses this controller.

1. Use the above list of DTC definitions and diagnostic tips to determine which controller is out of communication to check.
2. Ignition OFF, disconnect the harness connector at the controller that is not communicating.

Important: Only high speed GMLAN controllers have a serial line enable circuit OR an auxiliary serial line wakeup circuit. Refer to the controller diagrams to determine which controllers have these circuits. If the offending controller is missing one of these circuits, go to step 4.

3. Ignition ON, verify the test lamp illuminates between the serial link enable circuit OR the serial link auxiliary wakeup circuit and ground.
• If the test lamp does not illuminate, repair the open or high resistance in the circuit. If there are no open circuits, replace the BCM.
4. Ignition ON, test for a test lamp illuminated between all of the battery positive voltage circuits and ground.
• If the test lamp does not illuminate, repair the short to ground or open/high resistance in the circuit. If the circuit fuse is blown, also check the positive voltage outputs on the controller for a short to ground. If the circuits are OK, replace the failed controller.
5. Test for a test lamp illuminated between all ignition voltage circuits and ground.
• If the test lamp does not illuminate, repair the short to ground or open/high resistance in the circuit. If the circuit fuse is blown, also check the positive voltage outputs on the controller for a short to ground. If the circuits are OK, replace the failed controller.
6. Verify that the resistance between the controller ground circuits and ground is less than 1 ohm.
• If it is greater than 1 ohm, repair the open in the ground circuit.
7. Use the link list to determine if the offending controller is using a low speed GMLAN serial link.
• If the controller only uses high speed GMLAN, replace the controller.
8. Verify that the low speed GMLAN serial link circuit resistance between the offending controller and the controller issuing the DTC is less than 1 ohm.
• If resistance is greater than 1 Ω, test the low speed GMLAN serial link circuit for an open or high resistance.
9. If all circuits are OK, replace the controller with the communication problem.

• For information on replacing, configuring, and programming controllers, see "Controller Details"
• Replacing the GMLAN wiring

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Auxiliary serial line wakeup circuit	U1814	U0100	-	-

• The voltage in the system is 9 - 16 V.
• Serial communication is required for the vehicle power mode master to operate.

• The controllers use the default values of the missing parameters until the next ignition cycle.
• The controllers have never signaled, so certain subsystems will not work.
• The engine cannot be started.

• The current fault code is cleared after the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• Use the multimeter's MIN/MAX function to locate an intermittent fault.
• A short to ground can also cause multiple DTCs to be set "Communication failure" from controllers connected to a high speed GMLAN link.

1. Ignition OFF, disconnect the ECM and TCM harness connectors one at a time. After each disconnect, check for current DTCs. DTC U1814 should remain current.
• If the DTC is logged, replace the controller that was disconnected before the DTC was logged.
2. Ignition OFF, disconnect the harness connector at the BCM.
3. Test for infinite resistance between the auxiliary serial line wakeup circuit and ground.
• If the resistance is not infinite, repair the short to ground in the serial link circuit.
4. If all is well, replace the BCM.

Chain	Short circuit to ground	Open or increased resistance	Short circuit to supply voltage	Signal Characteristics
Enable Serial Link	U2099, U0100 - U0299?	U0100 - U0299	U0100 - U0299?	-
? The engine does not start. ? Only history. When removed, the DTC returns after a few ignition cycles.

Chain	normal range	Short circuit to ground	cliff	Short circuit to supply voltage
Operating conditions: Ignition switch in the ACC or RUN position
Enable Serial Link	ON	Turned off	ON	ON
Operating conditions: Ignition switch OFF
Enable Serial Link	Turned off	Turned off	Turned off	ON

• The voltage in the system is 9 - 16 V.
• Serial communication is required for the vehicle power mode master to operate.

• If there is a fault, the command output is turned off.
• The controllers use the default values of the missing parameters until the next ignition cycle.
• The controllers have never signaled, so certain subsystems will not work.
• The engine cannot be started while the circuit is shorted to ground.

• The current fault code is cleared after the fault disappears.
• The DTC is cleared from the log when the ignition cycle counter in the controller reaches the reset threshold of 50 without recurring the fault.

• Use the multimeter's MIN/MAX function to locate an intermittent fault.
• A short to ground will also result in multiple DTCs in the log "Communication failure" from controllers connected to a high speed GMLAN link.

1. Ignition OFF, disconnect the harness connector at the EBCM.
2. Check for current DTCs. DTC U2099 should remain current.
• If the DTC is logged, replace the EBCM.
3. Ignition OFF, disconnect the harness connector at the BCM.
4. Test for infinite resistance between the serial link enable circuit and ground.
• If the resistance is not infinite, repair the short to ground in the enable circuit.
5. If all is well, replace the BCM.