Scheme of the electronic engine control system: 1 - battery; 2 - ignition lock; 3 - electronic engine control unit (ECU); 4 - diagnostic block; 5 - absolute air pressure sensor in the intake manifold; 6 - air temperature sensor in the intake manifold; 7 - knock sensor; 8 - coolant temperature sensor; 9 - control relay of the cooling system fans; 10 - relay of the electric motor of the main fan; 11 - relay of the electric motor of the additional fan; 12 - electric fans of the cooling system; 13 - instrument cluster; 14 - phase sensor; 15 - diagnostic and control oxygen concentration sensors; 16 - rough road sensor; 17 - air conditioner compressor relay; 18 - air conditioning compressor; 19 - vehicle speed sensor; 20 - fuel pump relay; 21 - fuel module; 22 - solenoid valve purge adsorber; 23 - ignition coil; 24 - exhaust gas recirculation valve; 25 - idle speed regulator; 26 - throttle position sensor; 27 - nozzle; 28 - crankshaft position sensor
Elements of the electronic engine management system: 1* - rough road sensor; 2* - air temperature sensor in the intake manifold; 3* - phase sensor; 4* - crankshaft position sensor; 5* - throttle position sensor; 6 - nozzles; 7 - electronic control unit; 8 - absolute air pressure sensor; 9* - diagnostic block; 10 - ignition coil; 11* — speed sensor; 12 - mounting block of relays and fuses; 13* — coolant temperature sensor; 14* - diagnostic oxygen concentration sensor; 15 - spark plugs; 16 - control oxygen concentration sensor; 17* - knock sensor
* Item not visible in photo.
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 front panel.
Electronic engine control unit
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.
Signaling device of malfunction of a control system of the engine in a combination of devices
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.
The only exception is the crankshaft position sensor, if it malfunctions, the engine cannot work.
If the malfunction is temporary, the ECU will turn off the indicator after 10 seconds, provided that there are no other fault codes in the unit's memory that require the indicator to be turned on.
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 connected to the diagnostic block.
The diagnostic block is attached to the inside of the instrument panel console to the right of the gas pedal.
Diagnostic block
When deleting fault codes from the memory of the electronic unit using a diagnostic tool or by disconnecting the battery (for at least 10 s) the signaling device goes off.
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 mounted on the oil pump housing.
crankshaft position sensor
The sensor gives the ECU 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 driving disk near its core, which is combined with the auxiliary drive pulley.
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, a so-called "reference" synchronization pulse is generated in it.
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 the ignition coil.
The phase sensor is mounted on the rear wall of the camshaft bearing housing next to the camshaft pulley.
Phase sensor
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 the tide, made on the toe of the camshaft.
Depending on the angular position of the shaft, the sensor outputs rectangular voltage pulses 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 installed on the left side of the cylinder head.
coolant temperature sensor
The sensor is an NTC thermistor, i.e. its resistance decreases with increasing temperature.
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.
Throttle position sensor
A stabilized voltage of +5.0 V is supplied to one end of its resistive element from the ECU, and the other is connected to the "ground" of the electronic unit.
From the third output of the potentiometer (slider), which is connected to the throttle axis, a signal is received for the control unit.
By 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.
Absolute pressure sensor (rarefaction) air in the intake manifold is located in the engine compartment on the front panel and is connected to the intake manifold by a tube.
Intake manifold absolute pressure sensor
The sensor evaluates changes in air pressure in the intake manifold, which depend on the load on the engine, 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 (low vacuum in the intake manifold) 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 engine when atmospheric pressure changes depending on the altitude above sea level.
The air temperature sensor in the intake manifold is mounted in a corrugated air supply hose to the throttle assembly.
Intake air temperature sensor
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 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 mounted on the rear wall of the cylinder block in the area of the 3rd cylinder.
Knock sensor
The piezoceramic sensitive element of the sensor generates an AC voltage signal, the amplitude and frequency of which correspond to the vibration parameters of the engine 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.
The control oxygen concentration sensor is installed in the exhaust manifold.
Control oxygen sensor
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 cold, there is no output from the sensor 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.
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 sensor can be poisoned by the use of leaded gasoline.
The presence of lead compounds in 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.
Diagnostic oxygen sensor
The principle of operation of the diagnostic sensor is the same as that of the control oxygen concentration sensor.
To quickly warm up the sensor after starting the engine, a heating element is built into the sensor, which is controlled by the ECU.
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 vehicle speed sensor is mounted on the top of the gearbox housing, next to the gearshift mechanism.
Vehicle speed sensor
The principle of its operation is based on the Hall effect.
The sensor drive is installed in the gearbox and rotates at a frequency proportional to the speed of the front wheels of the vehicle.
The sensor sends out rectangular voltage pulses to the ECU (lower level - not more than 1.0 V, upper - not less than 5.0 V).
The same pulses are used to operate the car's speedometer.
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 rough road sensor is installed in the engine compartment on the right mudguard cup.
Rough road sensor
The sensor is designed to measure the amplitude of body vibrations.
The principle of its operation is based on the piezoelectric effect.
The variable load on the transmission that occurs when driving on rough roads affects the angular speed of rotation of the engine crankshaft.
At the same time, oscillations in the frequency of rotation of the crankshaft are similar to similar oscillations that occur during misfires of the air-fuel mixture in the engine cylinders.
In this case, to prevent false detection of misfires, the ECU disables this function of the on-board diagnostic system when the sensor signal exceeds a certain threshold.
The ignition system is part of the engine management system and consists of an ignition coil, high voltage wires and spark plugs.
In operation, the system does not require maintenance and adjustment, except for the replacement of candles.
The current control controls the fuel delivery by the injectors so that the composition of the working mixture is optimal for the efficient operation of the 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 cold, there is no output from the sensor 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.
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 sensor can be poisoned by the use of leaded gasoline.
The presence of lead compounds in 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 principle of operation of the diagnostic sensor is the same as that of the control oxygen concentration sensor.
To quickly warm up the sensor after starting the engine, a heating element is built into the sensor, which is controlled by the ECU.
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 vehicle speed sensor is mounted on the top of the gearbox housing, next to the gearshift mechanism.
The principle of its operation is based on the Hall effect.
The sensor drive is installed in the gearbox and rotates at a frequency proportional to the speed of the front wheels of the vehicle.
The sensor sends out rectangular voltage pulses to the ECU (lower level - not more than 1.0 V, upper - not less than 5.0 V).
The same pulses are used to operate the car's speedometer.
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 rough road sensor is installed in the engine compartment on the right mudguard cup.
The sensor is designed to measure the amplitude of body vibrations.
The principle of its operation is based on the piezoelectric effect.
The variable load on the transmission that occurs when driving on rough roads affects the angular speed of rotation of the engine crankshaft.
At the same time, oscillations in the frequency of rotation of the crankshaft are similar to similar oscillations that occur during misfires of the air-fuel mixture in the engine cylinders.
In this case, to prevent false detection of misfires, the ECU disables this function of the on-board diagnostic system when the sensor signal exceeds a certain threshold.
The ignition system is part of the engine management system and consists of an ignition coil, 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 coil is carried out by the ECU, depending on the mode of operation of the engine.
To the conclusions of the secondary (high voltage) coil windings are connected to candle wires: to one winding - 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).
Ignition coil
The ignition coil is non-separable, in case of failure it is replaced.
Spark plugs CHAMPION RN9YC, NGK BPR6ES or equivalents from other manufacturers.
Spark plug
The gap between the electrodes of the spark plug is 0.7–0.8 mm.
The size of the turnkey hexagon is 21 mm.
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.
When the engine is running, 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).
If there is no signal from the crankshaft position sensor (the shaft does not rotate, the sensor or its circuits are faulty) The ECU cuts off the fuel supply to the cylinders.
The fuel supply is also turned off when the ignition is turned off, which prevents the mixture from self-igniting in the engine cylinders.
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 coil (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 coil and the duration of the pulse supplied to the injectors decrease.
The ECU controls the fan through a relay (fans - if there is an air conditioner) cooling system depending on engine temperature and crankshaft speed.
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 the "negative" terminal of the battery).
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 the lugs of the "mass" wires on the engine are loose or dirty.