Since 2015, the VAZ-2123 car has been equipped with an electronic engine control system with a controller ME17.9.71 2123-1411020-50 to comply with EURO-5 toxicity standards.

Scheme of the electronic engine control system: 1 - battery, 2 - main relay, 3 - ignition switch, 4 - diagnostic oxygen concentration sensor, 5 - canister, 6 - air conditioning compressor, 7 - canister purge valve, 8 - concentration control sensor oxygen, 9 - nozzle, 10 - fuel rail, 12 - air filter, 13 - diagnostic connector, 14 - mass air flow sensor, 15 - tachometer, 16 - immobilizer unit, 17 - electronic gas pedal, 18 - throttle assembly, 19 - engine management system malfunction indicator lamp, 20 - phase sensor, 21 - ignition coil, 22 - coolant temperature sensor, 23 - controller, 24 - spark plug, 25 - crankshaft position sensor, 26 - right cooling fan, 27 - additional relay, 28 - right cooling fan relay, 29 - left cooling fan, 30 - left cooling fan relay, 31 - fuel pump relay, 32 - fuel filter tr, 33 - gravity valve, 34 - fuel module, 35 - speed sensor, 36 - knock sensor

The electronic engine control system (ECM) consists of a controller, sensors for engine and vehicle operation parameters, as well as actuators.

The controller is a mini-computer for special purposes, it consists of random access memory (RAM), programmable read-only memory (PROM) and electrically reprogrammable memory (EPROM).

RAM is used by the microprocessor to temporarily store current information about the operation of the engine (measured parameters) and calculated data.

Also, fault codes are recorded in the RAM.

This memory is volatile, i.e. when the power is interrupted (disconnecting the battery or disconnecting the wiring harness block from the controller), its contents are erased.

EPROM stores the engine control program, which contains a sequence of operating commands (algorithms) and calibration data (settings).

PROM determines the most important parameters of engine operation: the nature of the change in torque and power, fuel consumption, ignition timing, composition of exhaust gases, etc. PROM is non-volatile, i.e. the contents of its memory do not change when the power is turned off.

ERPROM stores controller, engine and vehicle IDs.

Records operating parameters as well as engine and vehicle malfunctions. It is a non-volatile memory.

The controller is the central unit of the engine management system.


It receives information from sensors and controls the actuators, ensuring optimal engine operation at a given level of vehicle performance.

The controller is located in the area of the passenger's feet and is attached to the bulkhead.

The controller controls actuators such as fuel injectors, motorized throttle, ignition coil, oxygen sensor heater, canister purge valve, and various relays.

The controller controls the on and off of the main relay (ignition relay), through which the supply voltage from the battery is supplied to the elements of the system (except for the electric fuel pump, electric fan, control unit and APS status indicator).

The controller turns on the main relay when the ignition is turned on.

When the ignition is turned off, the controller delays turning off the main relay for the time necessary to prepare for the next turn on (completion of calculations, setting the throttle to the position before starting the engine).

When the ignition is turned on, the controller, in addition to performing the functions mentioned above, exchanges information with the APS (if the immobilization function is enabled).

If as a result of the exchange it is determined that access to the car is allowed, then the controller continues to perform engine control functions.

Otherwise, the engine will be blocked.

The controller also performs a system diagnostic function.

It determines the presence of malfunctions of the system elements, turns on the alarm and stores codes in its memory that indicate the nature of the malfunction and help the mechanic to carry out repairs.

The engine control system uses a DMRV with a thermal anem metric type with digital output frequency response.

MAF (Mass Air Flow Sensor)

It is located between the air filter and the intake pipe hose.

The MAF signal is a frequency (Hz) signal, the pulse repetition rate of which depends on the amount of air passing through the sensor (increases with increasing air flow).

The scan tool reads the sensor as airflow in kilograms per hour.

Throttle Position Sensors (TPS)

Throttle assembly with throttle position sensor

Two TPSs are used in an EAF system.

TPS are part of the electric throttle.

TPDZ is a potentiometric type resistor, one of the outputs of which is supplied with a reference voltage (5 V) from the controller, and the second one is grounded from the controller.

From the output connected to the moving contact of the potentiometer, the output signal of the TPS is supplied to the controller.

The controller controls the throttle position electrically according to the position of the accelerator pedal.

According to the readings of the TPS, the controller monitors the position of the throttle valve.

When the ignition is turned on, the controller sets the damper to the pre-start position, the degree of opening of which depends on the temperature of the coolant.

In the pre-start position of the throttle valve, the output signal of TPS 1 should be within 0.65 ... 0.79 V, the output of TPS 2 should be within 4.21 ... 4.35 V.

If you do not start the engine and do not press the accelerator pedal within 15 seconds, the controller de-energizes the throttle pipe electric drive and the throttle valve is set to the position of 7-8% throttle opening.

In the de-energized state (LIMP HOME) of the throttle actuator, the output signal of TPS 1 is in the range of 0.80 ... 0.85 V, the output of TPS 2 is in the range of 4.15 ... 4.20 V.

Next, if no action is taken within 15 seconds, the mode of checking ("learning") the 0-position of the throttle valve will come - full closing and opening of the throttle valve to the pre-start position and then the throttle actuator will again switch to the de-energized mode.

At any throttle position, the sum of the TPS 1 and TPS 2 signals must be equal to (5 ± 0.1) V.

If a malfunction occurs in the TPS circuits, the controller de-energizes the throttle actuator, stores its code in its memory and turns on the signaling device.

In this case, the throttle valve is set to the position of 7-8% throttle opening.

Vehicles with an electronic throttle assembly use an electronic accelerator pedal that electrically transmits the accelerator pedal position signal to the controller.

Electronic Accelerator Pedal

The electronic gas pedal is located on a bracket under the driver's right foot.

The electronic gas pedal uses two accelerator pedal position (APPS) sensors.

DPPAs are potentiometric type resistors powered by a 5V controller.

The DPPA is mechanically connected to the drive from the pedal lever.

Two independent springs between the pedal arm and the body provide a return force.

Receiving an analog electrical signal from the ESA, the controller generates a signal to control the throttle position.

The output voltage of the DPPA changes in proportion to the pressing of the accelerator pedal.

When the accelerator pedal is released, the DPPA 1 signal should be within 0.46 ... 0.76 V, the DPPA 2 signal should be within 0.23 ... 0.38 V.

When the accelerator pedal is fully depressed, the DPPA 1 signal should be within 2.80 ... 3.10 V, the DPPA 2 signal should be within 1.40 ... 1.55 V.

At any position of the accelerator pedal, the signal of RPA 1 must be twice the signal of RPA 2.

Coolant temperature sensor (DTOZH)

The sensor is installed in the engine coolant flow, on the outlet pipe of the engine water jacket.

Coolant temperature sensor (CTOZH)

Sensor sensing element coolant temperature is a thermistor, i.e. a resistor whose electrical resistance changes with temperature.

High temperature causes low resistance, and low coolant temperature causes high resistance.

The controller outputs 5 V to the coolant temperature sensor circuit.

Knock Sensor (KD)

The knock sensor (DD) is installed on the cylinder block (Fig. 10).

The piezoceramic sensing element DD generates an AC voltage signal, the amplitude and frequency of which correspond to the engine vibration parameters.

When detonation occurs, the amplitude of vibrations of a certain frequency increases.

The controller at the same time corrects the ignition timing to dampen detonation.

Control oxygen sensor (UDC)

The most effective reduction in the toxicity of exhaust gases of gasoline engines is achieved with a mass ratio of air and fuel in the mixture (14.5 ... 14.6): 1.

Control Oxygen Sensor (ODC)

This ratio is called stoichiometric.

At this air-fuel ratio, the catalytic converter most effectively reduces the amount of hydrocarbons, carbon monoxide and nitrogen oxides emitted with exhaust gases.

To optimize the composition of the exhaust gases in order to achieve the greatest efficiency of the catalyst, closed-loop fuel control with feedback on the presence of oxygen in the exhaust gases is used.

Diagnostic Oxygen Sensor (DOC)

A catalytic converter is used to reduce the content of hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases.

The neutralizer oxidizes hydrocarbons and carbon monoxide, as a result of which they are converted into water vapor and carbon dioxide.

The neutralizer also recovers nitrogen from nitrogen oxides.

The controller monitors the redox properties of the converter by analyzing the signal from the diagnostic oxygen sensor installed after the converter.

Vehicle speed sensor provides a pulse signal that informs the controller about the speed of the vehicle. DSA is installed on the input shaft of the transfer case.

Vehicle Speed Sensor (DSA)

When the drive wheels rotate, the DSA generates 6 pulses per meter of vehicle movement.

The controller determines the vehicle speed from the pulse frequency.

The crankshaft position sensor is mounted on the camshaft drive cover at a distance of about 1 ± 0.4 mm from the top of the tooth of the drive disk mounted on the engine crankshaft.

Crankshaft position sensor (CKP)

The drive disc is integrated with the alternator drive pulley and is a gear wheel with 58 teeth in 6° increments and a "long" timing cavity formed by two missing teeth.

When the middle of the first tooth of the gear sector of the disk after the "long" cavity is aligned with the DPKV axis, the engine crankshaft is in position 114 ° (19 teeth) to the top dead center of the 1st and 4th cylinders.

When the master disk rotates, the magnetic flux in the magnetic circuit of the sensor changes, inducing alternating current voltage pulses in its winding.

The controller determines the position and frequency of rotation of the crankshaft by the number and frequency of these pulses and calculates the phase and duration of the pulses for controlling the injectors and the ignition coil.

The phase sensor is installed on the lug of the cylinder head.

Phase sensor (camshaft position sensor)

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

There is a special pin on the engine camshaft.

When the pin passes against the end of the sensor, the sensor outputs a voltage pulse to the controller low level (about 0 V), which corresponds to the position of the piston of the 1st cylinder in the compression stroke.

The phase sensor signal is used by the controller to organize sequential fuel injection in accordance with the order of operation of the engine cylinders.


Brake Light Switch is part of the brake pedal assembly and is designed to provide appropriate signals to the ECM when the driver presses/releases the brake pedal.

Brake Light Switch

In throttle-by-wire (E-gas) control systems, the brake pedal switch signals play an important role because they are used by the safety function of the ECM software.

For this reason, it is very important to ensure that the brake light switch is always in working order.

In the event of a discrepancy between its functional characteristic of switching, for example, in case of spontaneous changes in the values ​​of the adjustments specified in the instructions (due to vibrations of the brake pedal, wear of the switch and pedal block), the car engine may switch to emergency operation with a forcibly reduced power.

The Clutch Pedal Position Switch is part of the Clutch Pedal Assembly and is used to signal the ECM that the clutch pedal is depressed.

Clutch Pedal Position Switch

The switch has one group of contacts that switch voltage from terminal "15" of the ignition switch.

When the clutch pedal is depressed, the contacts are open.

The clutch pedal position switch signal is used by the ECM software to improve vehicle performance.