Description of the injection system and its elements

The engine control unit

power unit (engine and transmission) has electronic control in order to reduce emissions of toxic substances with exhaust gases while maintaining good handling and fuel efficiency. The center of the control system is the engine control unit (ECM). The ECM controls most engine and vehicle functions. The ECM constantly processes information from various sensors and performs diagnostics on various systems. If a malfunction is detected, the ECM informs the driver about this through the engine malfunction indicator (MIL) and writes the fault code to the memory block.

The engine control unit also supplies buffer voltage to the various sensors.

Engine malfunction indicator (MIL)

The malfunction indicator is located on the dashboard. The indicator can give a message about the need for engine maintenance (service engine soon) or one of the following symbols, which indicates that a malfunction has occurred in systems related to the management of emissions of harmful substances.



The following are the operating modes of the indicator:

• The indicator lights up after the ignition is turned on until the engine starts. This is a test for the performance of the indicator lamp.
• If there are no trouble codes in the ECM memory, the indicator goes out after starting the engine.
• If fault codes are stored in the ECM memory, the indicator remains on after starting the engine. The indicator goes out after three complete ignition cycles if the fault is no longer detected.
• The indicator flashes when a misfire is detected, which can damage the catalytic converter.

Cylinder deactivation system

The cylinder deactivation system consists of:

• oil collector;
• eight special valve lifters (two per cylinder to be deactivated);
• cylinder block generation GEN IV;
• engine control unit.

To ensure maximum fuel economy at low engine loads, the control unit includes a system for deactivating cylinders 1 and 7 of the left half-block and cylinders 4 and 6 of the right half-block, switching the engine to work according to the V4 scheme. The engine operates in a V8 pattern when starting the engine, when idling, and when operating at medium to high loads. The cylinders are deactivated by means of special tappets that prevent the intake and exhaust valves from opening, see the description of the timing drive system in chapter "Engine - mechanical part". The ECM limits the cylinder shutdown cycle to 10 minutes, then returns the engine to V8 for one minute. Switching between V8 and V4 circuits takes about 250 milliseconds.

Reasons for inhibiting cylinder shutdown:

• low vacuum in the intake manifold of the engine;
• insufficient vacuum in the brake booster;
• too sharp pressing the accelerator pedal;
• the position of the accelerator pedal is out of range;
• ignition voltage out of range;
• engine oil pressure out of range;
• engine oil temperature out of range;
• crankshaft speed out of range;
• incorrectly engaged automatic transmission gear;
• incorrect operating range of the automatic transmission;
• the gear shifting process is in progress;
• all cylinders are activated by the diagnostic scanner;
• it is not permissible to work for a short time according to the V8 scheme;
• exceeding the maximum operating time according to the V4 scheme;
• there is aeration of engine oil;
• the fuel cut-off system is activated;
• the fuel cut-off timer is activated;
• the temperature in the cabin is below the set (heating and air conditioning systems);
• the engine load limiting system is active;
• active braking torque control system;
• the system for limiting the transmission of torque to the axle is active;
• the engine overheat warning system is active;
• the catalytic converter overheat warning system is active;
• detonation combustion detection;
• the engine speed limitation warning system is active;
• the presence of fault codes:
• an absolute air pressure sensor in the intake manifold;
• engine oil pressure sensor;
• coolant temperature sensor;
• vehicle speed sensor;
• crankshaft position sensor;
• misfires;
• valve circuits of the cylinder shut-off system;

Throttle control

The throttle actuator control performs the following functions:

• determining the position of the accelerator pedal;
• setting the throttle position in accordance with the desire of the driver and the requirements of the movement;
• throttle position detection;
• conducting internal diagnostics;
• maintaining the set speed ("Cruise control");
• management of electrical energy consumption in the system.

The throttle control system includes:

• sensor (And) accelerator pedal position;
• throttle body;
• the engine control unit (ECM).

Accelerator pedal position sensor

The accelerator pedal assembly includes two individual pedal position sensors. Sensors are variable resistance included in three electrical circuits:

• reference voltage circuit 5 V;
• low reference voltage circuit;
• signal circuit;

The first sensor in when the accelerator pedal is released gives a signal below 1 V, when the pedal is pressed, the signal rises to a value of 4 V. The second sensor has signals of 0.5 and 2 V, respectively.

Throttle body

The throttle body assembly includes:

• throttle valve;
• electric motor of the throttle valve drive;
• two throttle position sensors.

The throttle valve is loaded with two springs; when the valve is closed, there is a small gap between it and the body. When the shutter is closed, the signal of the first sensor is 4 V, as the shutter opens, the signal decreases to 1 V. The signal of the second sensor changes vice versa.

Normal mode

During normal operation of the throttle actuator control system, the following functions are used:

• the minimum position of the accelerator pedal - when the engine control unit is turned on, the value of the signal corresponding to the minimum position of the pedal is updated;
• minimum throttle position - when the engine control unit is turned on, the throttle valve moves to the fully closed position and the value of the signal corresponding to this position of the damper is updated;
• "damper freezing" - if the throttle is not able to reach a certain minimum position, the mode is entered "freezing" dampers. In this mode, the control unit sends signals with the maximum pulse width several times to the drive motors in the direction of closing the damper;
• battery energy saving mode - after a certain time after the ignition is turned on without starting the engine, the control unit switches on the battery energy saving mode. In this mode, the voltage on the damper drive motor is minimal, and the damper is held in the closed position by springs.

Engine power reduction mode

When the control unit detects a malfunction in the throttle actuator system, the engine power reduction mode is activated. This mode can be recognized by the presence of the following phenomena:

• acceleration limitation - the control unit continues to use the accelerator pedal to control the throttle, however, vehicle acceleration is limited.
• throttle opening limitation - the control unit continues to use the accelerator pedal to control the damper, but the damper does not fully open;
• no reaction to the accelerator pedal - the control unit turns off the throttle motor, the damper returns to the closed position under the action of the springs;
• "forced idle" - the control unit performs the following actions:
• limits engine speed by either throttle position or fuel or spark timing control if the throttle is not moving.
• ignores the signals from the accelerator pedal position sensors.
• engine "stalls" - the control unit cuts off the fuel supply and the power supply to the throttle actuator.

Variable valve timing system

Variable valve timing system (camshaft position) - electro-hydraulic, which is used to improve the output parameters of the engine, in particular, reduce the emission of harmful substances, increase torque and reduce fuel consumption. When changing the position of the camshaft, the valve lift and the duration of the open position of the valves do not change. The entire range of variable valve timing is 62 degrees of rotation of the crankshaft (31 degrees camshaft rotation). For more information, see the description of the lubrication system in chapter "Engine - mechanical part".

The camshaft position is controlled according to the feedback scheme. The engine control unit uses the following data to calculate the camshaft position:

• engine speed;
• the magnitude of the vacuum in the intake manifold;
• angular position of the throttle valve;
• angular position of the camshaft;
• angular position of the crankshaft;
• the relative position of the crankshaft and camshaft;
• coolant temperature;
• engine oil pressure;
• engine oil level;
• the status of the solenoid valve circuit of the variable valve timing system.

Fuel system

Fuel system on early models with fuel return line (fuel pressure regulator mounted on the fuel rail). On later models, the fuel system is non-returnable. Here, the fuel pressure regulator is installed in the fuel pump module, which eliminates the need for a fuel return line from the engine, which in turn reduces the temperature in the fuel tank. Lowering the temperature in the fuel tank leads to a reduction in the emission of fuel vapors.

Fuel tanks

Fuel tanks are made of high-strength plastic. Front (or the only) The fuel tank is located on the left side of the vehicle. On dual tank models, the second fuel tank is located at the rear of the vehicle above the spare tire. Fuel tanks are attached with two metal straps.

The fuel filler neck has a built-in restrictor that prevents refueling with leaded gasoline.

When refueling in a dual fuel tank, fuel enters both tanks at the same time.



The filler neck is fitted with a tie-down cap fitted with a torque limiter.



To install the cover, turn the cover clockwise until it clicks into place. This indicates that the cap is properly installed and properly tightened. Incorrect installation of the cover will cause the evaporative emission system to malfunction.

Fuel pump module

The fuel pump module is installed in the fuel tank.

The fuel pump module contains:

• fuel level sensor;
• fuel pump;
• fuel filter;
• fuel tank pressure sensor (single tank or rear tank);
• fuel pressure control.

Front fuel pump module (or the only) fuel tank

Rear fuel tank fuel pump module

Operating modes of the fuel supply system

Start mode

After the ignition is turned on, the ECM energizes the fuel pump relay for two seconds to pressurize the fuel system. At this time, the ECM calculates the air-fuel ratio for starting based on signals from the coolant temperature, intake air flow/temperature, absolute air pressure, and throttle position sensors. The system remains in start mode until a certain RPM is reached, as determined by the ECM.

Overflow purge mode

If the engine "flooded" fuel, bleed the engine. To do this, press the accelerator pedal all the way and turn the engine over with the starter. Since the throttle is now fully open, the ECM reduces the fuel injector control pulse width to reduce fuel delivery. This state is maintained as long as the throttle remains wide open and the engine speed is still below the set value. When the throttle is closed, the system returns to start mode.

Work mode

The operating mode has two control states: with and without feedback. When the engine has just started and the engine speed is above normal idle (warming up), the system operates according to the scheme without feedback, i.e. The ECM ignores the signals from the oxygen sensors. The ECM now calculates the air-fuel ratio based on signals from the coolant temperature, intake air flow/temperature, absolute air pressure, and throttle position sensors. The system operates without feedback until the following condition occurs:

• both front oxygen sensors will not show an alternating signal, which means that both sensors are warm enough;
• the engine temperature has reached a certain value;
• enough time has elapsed since the engine started to warm up.

All the above values for each specific engine are different and are stored in the EEPROM memory. After reaching the above state, the system enters the feedback control mode, maintaining the stoichiometric air-fuel ratio.

Overclocking mode

When the driver presses the accelerator pedal hard, the air flow through the engine increases. To prevent possible lean mixture and subsequent "failure" in engine operation, ECM (based on signals from different sensors) increases the width of the control pulse by the fuel injectors to a slight enrichment of the mixture, which is necessary for dynamic acceleration.

Deceleration mode

When the driver releases the accelerator pedal, the air flow through the engine decreases. The ECM reduces fuel delivery to the point of shutting it off if rapid deceleration is required or under engine braking. Shutting off the fuel supply prevents damage to the catalytic converters.

Battery voltage correction mode

When the battery voltage is low, the ECM compensates for low spark power in the following ways:

• increase in fuel supply;
• increase in idle speed;
• increasing the rest time of energy accumulation in the secondary winding of the ignition coil.

Fuel cut mode

The ECM cuts off the fuel supply in the following conditions:

• ignition off. This prevents the engine from glowing ("dieseling");
• the ignition is on, but there is no ignition reference signal. This prevents "overflow" fuel or backfires;
• engine speed is higher than allowed;
• the vehicle speed is too high, higher than the calculated tire speed;
• under engine braking at high speed. This reduces hydrocarbon emissions and prevents flashbacks;
• during prolonged deceleration. This prevents damage to the catalytic converters.

Ignition system

The ignition system includes:

• Crankshaft Position Sensor Timing Ring - The crankshaft position sensor timing ring is part of the crankshaft. The ring has 58 teeth and a support gap. Ring teeth are evenly spaced in 6-degree increments. The two missing teeth create a gap of 12 degrees, which is used to create a timing reference that recognizes the TDC of the first cylinder. The timing pulse is used by the ECM to determine the ignition timing for a specific cylinder in the engine's firing order.
• Crankshaft position sensor.
• Camshaft Position Sensor Timing Ring - The camshaft position sensor timing ring is part of the camshaft sprocket. The ring has two narrow teeth and 2 wide teeth located around the circumference of the ring. front (or rear) the edges of these 4 teeth give gaps of 90 degrees. The ECM uses signals from narrow and wide teeth to determine the position of the camshaft, which cylinder is on the compression or expansion stroke, and the relative position of the crankshaft and camshaft.
• Camshaft position sensor.
• Ignition Coils - Eight ignition coils are used in total (one per cylinder).
• The engine control unit (ECM) - The ECM controls all functions of the ignition system and continuously adjusts the ignition timing. The ECM determines ignition timing based on readings from the throttle position, coolant temperature, air flow/temperature, vehicle speed, automatic transmission gear, and knock sensors.

Speed control system

The cruise control maintains the desired vehicle speed at speeds above 40 km/h.

The speed control system includes:

• accelerator pedal;
• brake light switch (brake pedals);
• body electrical control unit (VSM);
• cruise control switches;
• the engine control unit (ECM);
• electric motor of the throttle valve drive;
• vehicle speed sensor.

The cruise control system is activated and controlled by switches located on the steering wheel:

• ON/OFF switch (ON OFF)
• switch +RES
• switch -SET

Switch signals are processed by the body electrical control unit (VSM). The BCM transmits the status of the system switch to the engine control unit (ECM) through the GMLAN serial data circuit. Based on the received data, the ECM determines and maintains the desired vehicle speed by controlling the throttle actuator.

Turn the ON/OFF switch to the ON position to turn on the system (ON) and immediately press the SET switch. The engine control module determines the current vehicle speed and sends a message to the driver information display via the GMLAN bus. Cruise set to