The electronic engine control system is a complex system designed for the preparation of an air-fuel mixture in a certain proportion and quantity required for various engine operating modes
The system ensures compliance with modern standards on emission toxicity and vapors while maintaining high driving performance and low fuel consumption.
The control device in the system is an electronic control unit (ECU, controller).
Based on the information received from the sensors, the ECU calculates the parameters of fuel injection regulation and ignition timing angle control.
In addition, in accordance with the algorithm laid down, the ECU controls the electric motor of the engine cooling system fan and the electromagnetic clutch of the air conditioner compressor, performs the function of self-diagnosis of system elements and notifies the driver of malfunctions.
In case of failure of individual sensors and actuators, the ECU switches on emergency modes that ensure the engine"s operability.
The amount of fuel supplied by the injectors is determined by the duration of the electrical signal from the ECU.
The electronic unit monitors the engine status data, calculates the fuel demand and determines the required duration of fuel supply by injectors (signal duration).
To increase the amount of fuel supplied, the duration of the signal increases, and to reduce the fuel supply, it decreases.
The engine control system, along with the electronic control unit, includes sensors, actuators, connectors and fuses.
The electronic control unit is connected by electrical wires to all sensors of the system.
Receiving information from them, the unit performs calculations in accordance with the parameters and control algorithm stored in the memory of a programmable permanent storage device (PPZU), and controls the system"s actuators.
The version of the program recorded in the memory of the CPU is indicated by the number assigned to this modification of the ECU.
The control unit detects the fault, identifies and remembers its code, even if the failure is unstable and disappears (for example, due to poor contact).
The engine control system malfunction alarm in the instrument cluster goes out 10 seconds after the failed node is restored to working capacity.
After repair, the fault code stored in the memory of the control unit must be erased.
To do this, turn off the power supply of the unit for 10 seconds (remove the fuse of the power supply circuit of the electronic control unit or disconnect the wire from the terminal "minus" of the battery).
The unit supplies DC voltage of 5 and 12 V to various sensors and switches of the control system.
Since the electrical resistance of the power supply circuits is high, the indicator lamp connected to the system terminals does not light up.
To determine the supply voltage at the terminals of the ECU, a voltmeter with an internal resistance of at least 10 mOhm should be used.
The ECU is not suitable for repair, so in case of failure it must be replaced.
The crankshaft position sensor is designed to synchronize the operation of the electronic engine control unit with the angular position of the crankshaft.
The sensor action is based on the Hall effect.
The sensor is installed in the rear of the engine opposite the driving crown on the flywheel. The driving crown is a gear wheel with depressions.
Two teeth are cut off to create a synchronization pulse ("reference" pulse), which is necessary to coordinate the operation of the control unit with the TDC of the pistons in the 1st and 4th cylinders.
When the crankshaft rotates, the teeth change the magnetic field of the sensor, inducing AC voltage pulses.
The control unit uses the sensor signals to determine the speed of rotation of the crankshaft and outputs pulses to the injectors.
If the sensor fails, the engine cannot be started.
The camshaft position sensor of the inductive type is installed in the front of the cylinder head.
When the intake camshaft rotates, the projections on its front neck change the magnetic field of the sensor, inducing AC voltage pulses.
Sensor signals are used by the ECU to organize phased fuel injection in accordance with the order of operation of the cylinders, as well as to control the change of valve timing phases depending on the operating mode of the engine.
If a malfunction occurs in the circuit of the camshaft position sensor, the electronic unit stores its code in memory and turns on the engine control system malfunction alarm.
The coolant temperature sensor is installed in the engine cooling system.
The sensor"s sensing element is a thermistor whose electrical resistance varies inversely with temperature.
At a low temperature of the coolant (-20 ° C), the resistance of the thermistor is about 15 kOhm, when the temperature rises to +80 ° C, the resistance decreases to 320 ohms.
The electronic unit supplies the temperature sensor circuit with a constant "reference" voltage. The voltage of the sensor signal reaches its maximum value on a cold engine and decreases as it warms up.
According to the voltage value, the electronic unit determines the engine temperature and takes it into account when calculating the adjustment parameters of injection and ignition.
In case of sensor failure or irregularities in the circuit of its connection, the ECU sets the fault code and remembers it.
An additional thermistor is also installed in the sensor housing to control the coolant temperature indicator in the instrument cluster.
The throttle position sensor is mounted on the body of the throttle assembly and is connected to the throttle axis.
The sensor is a potentiometer, one end of which is supplied with a "plus" supply voltage (5 V), and the other end is connected to the "mass" From the third output of the potentiometer (from the slider) there is an output signal to the electronic control unit.
When the throttle valve turns (due to the impact on the drive pedal), the voltage at the sensor output changes. When the throttle is closed, it is below 0.5 V.
When the flap opens, the voltage at the sensor output increases, with the flap fully open, it should be more than 4 V.
By monitoring the output voltage of the sensor, the ECU adjusts the fuel supply depending on the throttle opening angle (i.e. at the request of the driver).
The throttle position sensor does not require adjustment, since the control unit perceives idling (i.e. full throttle closure) as a zero mark.
The oxygen concentration control sensor is used in a feedback injection system and is installed in the intake pipe.
To adjust the calculations of the injection pulse duration, information about the presence of oxygen in the exhaust gases is used, this information is provided by the oxygen concentration control sensor.
The oxygen contained in the exhaust gases reacts with the sensor, creating a potential difference at the sensor output.
It varies from approximately 0.1 V (high oxygen content - poor mixture) to 1 V (low oxygen content – rich mixture).
By monitoring the output voltage of the oxygen concentration sensor, the ECU determines which command to correct the composition of the working mixture to supply to the injectors.
If the mixture is poor (low potential difference at the sensor output), then the controller gives the command to enrich the mixture; if the mixture is rich (high potential difference), to deplete the mixture.
The diagnostic oxygen concentration sensor works on the same principle as the control sensor.
The signal generated by the diagnostic oxygen concentration sensor indicates the presence of oxygen in the exhaust gases after the neutralizer.
If the neutralizer is working normally, the readings of the diagnostic sensor will differ significantly from the readings of the control sensor.
Information from each sensor enters the control unit in the form of low (from 0.1 V) and high (up to 0.9 V) level signals.
When the signal is low, the control unit receives information about the high oxygen content. A high level signal indicates a low oxygen content in the exhaust gases.
By constantly monitoring the voltage of the sensor signal, the control unit corrects the amount of fuel injected by the injectors.
At a low signal level of the sensor at the entrance to the collector (poor fuel-air mixture), the amount of fuel supplied increases, at a high signal level (rich mixture) - decreases.
The detonation sensor is attached to the upper part of the cylinder block in the zone between the 2nd and 3rd cylinders and detects abnormal vibrations (detonation shocks) in the engine.
The sensitive element of the detonation sensor is a piezocrystalline plate.
During detonation, voltage pulses are generated at the sensor output, which increase with increasing intensity of detonation shocks.
The electronic unit adjusts the ignition timing according to the sensor signal to eliminate detonation flashes of fuel.
During operation, the ECU also uses the vehicle speed data received from the ABS control unit.
On versions of the car that are not equipped with ABS, a speedometer sensor installed in the gearbox or a separate speed sensor of the right front wheel is used for this purpose.
The absolute pressure sensor in the intake pipe converts the degree of vacuum in this pipe into a change in the electrical voltage, by the value of which the ECU sets the parameters of the engine.
The sensor is mounted on the intake pipe.
The output voltage of the sensor varies according to the pressure in the intake pipe - from 4.0 V (with the throttle valve fully open) to 0.79 V (with the flap closed).
When the engine is not running, the sensor voltage control unit detects atmospheric pressure and adapts the injection control parameters to a specific altitude above sea level.
The atmospheric pressure values stored in memory are periodically updated during the uniform movement of the car and during the full opening of the throttle valve.
The solenoid valve of the valve timing system is installed in the cylinder head of the engine.
The valve regulates the oil pressure supplied to the phase change actuator mounted at the front end of the intake valve camshaft.
The system performs optimal adjustment of the timing phases, changing them over the entire range of engine frequency and load values, which increases power and torque at any speed.
When the engine is stopped, the oil pressure forces the control valve spool to move to the position corresponding to the latest gas distribution phase.
The control valve is triggered by a signal from the engine control unit and supplies oil either to the delay chamber or to the advance chamber with a continuous change in the timing phases, respectively, either in the direction of their advance or in the direction of delay.
A diagnostic connector is used to output fault codes detected during the operation of the engine control system from the ECU memory.
The diagnostic connector is located in the car interior on the left side under the decorative cover of the mounting block.
A scanning device can be connected to the diagnostic connector, which reads information from the serial data bus.