Engine control system device

Electronic engine control unit.

The engine is equipped with a distributed phased fuel injection system: gasoline is supplied by injectors to each cylinder in turn in accordance with the engine operation order.

The engine management system consists of an electronic control unit (ECU), sensors for engine and vehicle operation parameters, as well as actuators.

The ECU is a mini-computer for special purposes. It contains a working memory (RAM) and programmable read only memory (PROM).

The ECU is located in the engine compartment - it is attached with a bracket to the left mudguard. In addition to supplying voltage to the sensors and controlling actuators, the ECU performs diagnostic functions of the engine management system (onboard diagnostic system) - determines the presence of malfunctions of elements in the system, turns on the malfunction indicator in the instrument cluster and stores fault codes in its memory. If a malfunction is detected, in order to avoid negative consequences (burnt pistons due to detonation, damage to the catalytic converter in the event of a misfire in the air-fuel mixture, exceeding the limit values for exhaust gas toxicity, etc.), the ECU puts the system into emergency operating modes.


Their essence is that in case of failure of any sensor or its circuit, the engine control unit uses replacement data stored in its memory.



The engine management system malfunction indicator is located in the instrument cluster.

If the system is working, then when the ignition is turned on, the warning lamp should light up - thus, the ECU checks the serviceability of the warning lamp and the control circuit.

After starting the engine, the indicator should go out if there are no conditions for its activation in the computer memory. Turning on the signaling device when the engine is running informs the driver that the on-board diagnostic system has detected a malfunction, and further movement of the car occurs in emergency mode.

In this case, some parameters of the engine may deteriorate (power, efficiency, efficiency), but movement with such malfunctions is possible, and the car can independently drive to the service station.

If the fault was temporary, the electronic control unit will turn off the warning lamp for three trips without a fault.

Fault codes (even if the warning light is off) remain in the memory of the unit and can be read using a special diagnostic tool - a scanner connected to the diagnostic block.






Diagnostic block (diagnostic connector) located under the instrument panel - attached with two self-tapping screws to the instrument panel frame bracket (slightly to the right of the hood latch handle).

When the fault codes are cleared from the memory of the electronic unit using the diagnostic tool, the malfunction indicator lamp in the instrument cluster goes out.

The sensors of the control system give the ECU information about the parameters of the engine and the car, on the basis of which it calculates the moment, duration and order of opening of the fuel injectors, the moment and order of sparking.





The crankshaft position sensor is located on the front wall of the cylinder block under the oil filter.




The sensor provides the controller with information about the speed and angular position of the crankshaft.

The sensor is of an inductive type, it reacts to the passage of the teeth of the drive disk attached to the cheek of the crankshaft of the 4th cylinder near its core. The teeth are located on the disk with an interval of 6°. To determine the position of the crankshaft, two teeth out of 60 are cut off, forming a wide groove.

When this groove passes by the sensor, the so-called «reference» sync pulse. The installation clearance between the sensor core and the tooth tips is approximately 1.3 mm. When the driving disk rotates, the magnetic flux in the magnetic circuit of the sensor changes - alternating current voltage pulses are induced in its winding. Based on the number and frequency of these pulses, the ECU calculates the phase and duration of the pulses for controlling the injectors and ignition coils.

Phase sensor (camshaft position) attached to the right end of the cylinder head next to the exhaust camshaft pulley.







Mutual position of the phase sensor and the exhaust camshaft pulley

The signal from the phase sensor is used by the ECU to coordinate the fuel injection processes in accordance with the order of operation of the cylinders.

The principle of operation of the sensor is based on the Hall effect.

The sensor responds to the passage of a protrusion made at the end of the camshaft pulley to determine the position of the piston of the first cylinder during the working cycle. Depending on the angular position of the shaft, the sensor outputs rectangular voltage pulses of different levels to the control unit. Based on the output signals of the crankshaft and camshaft position sensors, the control unit sets the ignition timing and the cylinder into which fuel should be supplied. If the phase sensor fails, the ECU switches to the non-phased fuel injection mode.



The coolant temperature sensor is screwed into the threaded hole in the rear wall of the cylinder head, between the air supply channels of the 1st and 2nd cylinders. The sensor rod is washed by the coolant circulating through the cooling jacket of the cylinder head.

The sensor is an NTC thermistor, i.e. its resistance decreases as the temperature rises. The ECU supplies a stabilized voltage of +5.0 V to the sensor through a resistor and, based on the voltage drop across the sensor, calculates the coolant temperature, the values of which are used to adjust the fuel supply and ignition timing.

The throttle position sensor is mounted on the throttle shaft and is a potentiometric type resistor.

A stabilized voltage of +5.0 V is supplied to one end of its resistive element from the computer, and the other is connected to «weight» electronic block. From the third output of the potentiometer (slider), which is connected to the throttle axis, a signal is received for the control unit. By periodically measuring the output voltage of the sensor signal, the ECU determines the current throttle position to calculate the ignition timing and the duration of the fuel injection pulses, as well as to control the idle speed controller. The throttle position sensor and idle speed control are combined into one unit, mounted on the throttle assembly.









If the sensor fails, it is necessary to replace the entire throttle assembly with the idle speed control unit and the throttle position sensor (see Removing the throttle assembly).



Absolute pressure sensor (rarefaction) air in the intake manifold is attached to the intake manifold body and connected by a tube to its receiver. The sensor evaluates changes in air pressure in the intake manifold, which depend on the load on the engine and the speed of its crankshaft, and converts them into voltage output signals. Based on these signals, the ECU determines the amount of air entering the engine and calculates the required amount of fuel. To supply more fuel at a large throttle angle (vacuum in the intake manifold is negligible) The ECU increases the operating time of the fuel injectors.

With a decrease in the throttle opening angle, the vacuum in the intake manifold increases, and the ECU, processing the signal, reduces the operating time of the injectors. The intake manifold absolute pressure sensor allows the ECU to make adjustments to the operation of the engine when atmospheric pressure changes depending on the altitude above sea level.



The engine intake air temperature sensor is screwed into the threaded hole in the intake pipe receiver. The sensor is a thermistor (with the same electrical characteristics as the coolant temperature sensor), which changes its resistance depending on the air temperature. The ECU applies a stabilized voltage of +5.0 to the sensor through a resistor and measures the change in signal level to determine the intake air temperature.

The signal level is high when the air in the pipeline is cold and low when the air is hot.

The information received from the sensor is taken into account by the ECU when calculating the air flow to correct the fuel supply and the ignition timing.



The knock sensor is attached to the rear wall of the cylinder block in the area of the 3rd cylinder.

The piezoceramic sensitive element of the sensor generates an alternating voltage signal, the amplitude and frequency of which correspond to the vibration parameters of the engine cylinder block wall. When detonation occurs, the amplitude of vibrations of a certain frequency increases. At the same time, to suppress detonation, the ECU corrects the ignition timing in the direction of a later one.

In the engine management system, two oxygen concentration sensors are used - control and diagnostic.





The control oxygen concentration sensor is installed in the exhaust manifold.

The sensor is a galvanic current source, the output voltage of which depends on the oxygen concentration in the environment surrounding the sensor. Based on a signal from the sensor about the presence of oxygen in the exhaust gases, the ECU adjusts the fuel supply by the injectors so that the composition of the working mixture is optimal for the efficient operation of the exhaust gas catalytic converter.

The oxygen contained in the exhaust gases, after entering into a chemical reaction with the sensor electrodes, creates a potential difference at the sensor output, varying from approximately 0.1 V to 0.9 V.

Low signal level means lean mixture (presence of oxygen), and a high level is rich (no oxygen). When the sensor is in a cold state, there is no sensor output signal, because its internal resistance in this state is very high - several MΩ (engine management system operates in open loop).

For normal operation, the oxygen concentration sensor must have a temperature of at least 300°C.

In order to quickly warm up the sensor after starting the engine, a heating element is built into the sensor, which is controlled by the ECU. As the sensor warms up, the resistance drops and it begins to generate an output signal. Then the ECU starts to take into account the signal from the oxygen concentration sensor for fuel control in closed loop mode.

The oxygen concentration sensor can be «poisoned» as a result of the use of leaded gasoline or the use of sealants containing large amounts of silicone when assembling the engine (silicon compounds) with high volatility. Silicone vapors can enter through the crankcase ventilation system into the combustion chamber of the engine. The presence of lead or silicon compounds in the exhaust gases can lead to sensor failure.

In the event of a failure of the sensor or its circuits, the ECU controls the fuel supply in an open loop.

The diagnostic oxygen sensor is installed after the catalytic converter in the intermediate pipe of the exhaust system. The main function of the sensor is to evaluate the efficiency of the exhaust gas catalytic converter.

The signal generated by the sensor indicates the presence of oxygen in the exhaust gases after the catalytic converter. If the catalytic converter is operating normally, the diagnostic sensor reading will differ significantly from the control sensor reading.

The principle of operation of the diagnostic sensor is the same as that of the control oxygen concentration sensor.



The vehicle speed sensor is mounted on the transmission clutch housing from above, next to the gearshift mechanism.

The principle of operation of the speed sensor is based on the Hall effect.

The sensor drive gear is engaged with the gear mounted on the differential box. The sensor outputs rectangular voltage pulses to the computer with a frequency proportional to the speed of rotation of the drive wheels. The number of sensor pulses is proportional to the distance traveled by the vehicle.

The ECU determines the speed of the car by the frequency of the pulses.

The ignition system is part of the engine management system and consists of two ignition coils, high voltage wires and spark plugs. In operation, the system does not require maintenance and adjustment, except for the replacement of candles.



The control of the current in the primary windings of the coils is carried out by the electronic unit, depending on the operating mode of the engine.

To the conclusions of the secondary (high voltage) the coil windings are connected to candle wires: to one coil - the 1st and 4th cylinders, to the other - the 2nd and 3rd. Thus, the spark simultaneously jumps in two cylinders (1–4 or 2–3) - in one at the end of the compression stroke (working spark), in the other - at the end of the release cycle (single).

The ignition coil is non-separable, in case of failure it is replaced.



Spark plugs NGK BKR6 E-11 (1.4 l and 1.6 l engines) and NGK BKUR6ETB (engine 1.8 l) or equivalents from other manufacturers.

Gap between spark plug electrodes 1.0–1.1 mm (1.4 l and 1.6 l engines) and 0.7–0.9 mm (engine 1.8 l).

The size of the hexagon of the candle - under the head «at 16».

When the ignition is turned on, the ECU energizes the fuel pump relay for 2 seconds to create the necessary pressure in the fuel rail. If during this time cranking of the crankshaft by the starter has not begun, the ECU turns off the relay and turns it on again after the start of cranking.

If the engine has just been started and its speed is above 400 min¯¹, the control system operates in an open loop, ignoring the signal from the control oxygen concentration sensor. At the same time, the ECU calculates the composition of the air-fuel mixture based on the input signals from the coolant temperature sensor and the air intake manifold absolute pressure sensor. After warming up the control oxygen concentration sensor, the system starts to work in a closed loop, taking into account the sensor signal.

If, when trying to start the engine, it does not start and there is a suspicion that the cylinders are flooded with excess fuel, they can be purged by fully depressing the pedal «gas» and turning on the starter. At this throttle position and crankshaft speed below 400 min¯¹, the ECU will turn off the injectors. When the pedal is released «gas», when the throttle is less than 80% open, the ECU will turn on the injectors.

When the engine is running, depending on the information coming from the sensors, the composition of the mixture is regulated by the duration of the control pulse applied to the injectors (the longer the pulse, the greater the fuel supply).

During engine braking (with gear and clutch engaged), When the throttle is fully closed and the engine speed is high, no fuel injection is performed to reduce exhaust emissions.

When the voltage drops in the vehicle's on-board network, the ECU increases the energy accumulation time in the ignition coils (for reliable ignition of the combustible mixture) and injection pulse duration (to compensate for the increase in nozzle opening time). With an increase in the voltage in the on-board network, the energy accumulation time in the ignition coils and the duration of the pulse supplied to the injectors decrease.

When the ignition is turned off, the fuel supply is turned off, which prevents the mixture from spontaneous ignition in the engine cylinders.

When servicing or repairing the engine management system, always turn off the ignition (in some cases it is necessary to disconnect the wire terminal from «negative» battery terminal). When carrying out welding work on a vehicle, disconnect the engine management system wiring harnesses from the ECU. Before drying the car in a drying chamber (after painting) remove the computer.

With the engine running, do not disconnect or adjust the engine control harness connectors or the battery terminals. Do not start the engine if the wire terminals on the battery terminals and lugs «massive» wires on the motor are loose or dirty.