Engine management system device (VAZ-2112)

Engine management system turns the fuel pump on and off, controls the amount of air entering the engine cylinders, injects the required amount of fuel into the intake manifold, controls the formation of grease on the spark plugs, adjusts the ignition timing, regulates the crankshaft speed at idle, controls the electric fan of the engine cooling system. The engine management system is electronic, with distributed phased fuel injection (that is, fuel is injected into the intake manifold of each cylinder in accordance with the engine's working cycle) [On some 2111 engines the injection is unphased.] The system consists of the following elements:

• electronic control unit;
• sensors:
• 1) crankshaft position sensor;
• 2) camshaft position sensor [On vehicles with phased injection.];
• 3) throttle position sensor;
• 4) knock sensor;
• 5) coolant temperature sensor;
• 6) mass air flow sensor;
• 7) vehicle speed sensor;
• 8) oxygen concentration sensor (or two sensors for EURO III);
• 9) Rough road sensor (for EURO III);
• actuators:
• 1) main relay;
• 2) fuel pump relay;
• 3) injectors;
• 4) ignition coil or ignition module [The ignition module was installed on cars with 2111 engines of the first years of production; on cars with 21124 engines, four individual coils are installed.];
• 5) idle speed controller;
• 6) relay of the electric fan of the cooling system;
• 7) Engine management system malfunction indicator lamp;
• 8) purge valve of the adsorber;
• connecting wires;
• diagnostic connector block.

The engine management system also integrates:

• car anti-theft system;
• speedometer;
• tachometer.

The main control element of the system is the electronic control unit (ECU), or, as it is often called, a controller with a built-in microprocessor. In essence, the ECU is a specialized mini-computer in which only one program is installed - engine control, and the sensors and actuators form the peripheral equipment of this computer. The unit receives and analyzes signals from the sensors. Based on the received data, the unit calculates control commands and issues them to the actuators. The unit has three types of memory [The design of the ECU may be changed by the manufacturer.]: read-only memory (ROM), random access memory (RAM) and reprogrammable memory (EPROM).







ROM - non-volatile memory (that is, the information in the memory is retained when the power is turned off) and is a microcircuit ("chip") [The design of the ECU may be modified by the manufacturer.]. The microcircuit is installed on the unit board via a detachable connection - a special block, and is not soldered, like other elements. This is done in order to unify the ECU for different car models. The ROM stores the calculation program and the data necessary for the calculation (engine parameters, transmission ratios and other characteristics). This information is individual for each vehicle modification.



The ECU, immobilizer control unit, fuses and relays of the engine management system are located under the instrument panel console.

Note: The right instrument panel console trim has been removed.

Warning! Unqualified reprogramming of ROM or replacement of a chip from another car model (so-called chip tuning) may lead to engine malfunctions, failure of engine control system components, and engine damage.

During operation, the ECU monitors the serviceability of all elements and circuits of the engine management system. Having detected a malfunction, the ECU switches the engine management system to the backup mode and turns on the engine malfunction indicator lamp on the instrument panel. The engine can continue to operate (except in case of crankshaft position sensor failure, see below), which allows you to get to the repair site under your own power. The ECU records the codes of detected faults in RAM. The operational information that the ECU microprocessor uses in calculations is also stored there. When the battery is disconnected from the vehicle's on-board network, all information stored in RAM will be deleted.

The EPROM stores the codes of the car's anti-theft system (immobilizer). This type of memory is non-volatile. After the immobilizer is activated, the ECU blocks the operation of the engine management system when trying to start the engine without special electronic keys.

The crankshaft position sensor (CPS) is designed to generate signals by which the ECU synchronizes its operation with the engine cycles. That is why this sensor is often called a synchronization sensor. The sensor operates on the principle of induction - when the crankshaft pulley teeth pass the sensor core, AC voltage pulses occur in the sensor circuit. The pulse frequency corresponds to the crankshaft rotation frequency. The teeth are located around the pulley circumference (6° apart). Two of them are spaced at an angular distance of 18°. This is done to generate reference signals in the sensor circuit - a kind of reference points relative to which the ECU determines the position of the crankshaft - the top dead centers in the first/fourth and second/third cylinders. The engine cannot operate with a faulty crankshaft position sensor. The crankshaft position sensor cannot be repaired - in case of a malfunction, it is replaced as an assembly.



The camshaft position sensor (CPS) is designed to generate a signal by which the ECU determines the top dead center (TDC) of the piston of the first cylinder during the compression stroke. Sometimes this sensor is called a phase sensor. The operating principle of the sensor is based on the Hall effect. When a protrusion of the ring fixed to the pulley of the camshaft of the intake valves passes through a slot in the end of the sensor, the sensor sends an electric signal to the ECU. If the CPS is faulty, the electronic control unit switches the system to the backup mode.

The camshaft position sensor is an electronic device that cannot be repaired. If the sensor is faulty, it must be replaced.



The camshaft position sensor is installed in the cylinder head plug on 8-valve engines (2111 and 21114)



The camshaft position sensor is mounted on the cylinder head near the rear timing belt cover on 16-valve engines (2112 and 21124)

The knock sensor (DS) is a piezoelectric sensor that reacts to engine vibration and is installed on the front wall of the cylinder block. Based on the sensor signals, the ECU determines the moment of detonation during engine operation and adjusts the ignition timing accordingly. If the DS malfunctions, the electronic control unit switches the system to the backup mode.



Mass Air Flow Sensor (MAF) film type, installed between the air filter and the throttle valve. Based on the sensor signal, the ECU calculates the amount of air entering the engine cylinders. If the MAF is faulty, the electronic control unit switches the system to backup mode.



Throttle Position Sensor (TPDZ) is installed on the throttle body and is connected to the throttle axis. TPDZ is a variable resistor, the resistance of which depends on the angle of the throttle position. Based on the TPDZ signal, the electronic control unit determines the amount of throttle opening. If TPDZ is faulty, the electronic control unit switches the system to backup mode.



Idle speed control valve (IAC) is a shut-off valve driven by a stepper motor. The IAC is installed on the throttle body. The ECU, by sending a controlled signal to the IAC, regulates the engine crankshaft speed at idle, when starting and warming up the engine.



Oxygen concentration sensor provides an output signal, which the ECU uses to determine the oxygen concentration in the exhaust gases. Based on the data received, the ECU adjusts the amount of fuel injected into the engine cylinders, thereby maintaining the optimal air-fuel mixture ratio (this is necessary for the efficient operation of the catalytic converter). The oxygen concentration sensor's sensitive element is located in the exhaust gas flow (before the catalytic converter). The sensor can only operate when its sensitive element is heated to a temperature of at least 300°C. To reduce the warm-up time, a heating element is built into the sensor. On engines 2111 and 2112, the sensor is installed in the lower part of the intake pipe, and on engines 21114 and 21124 - in the upper part of the exhaust manifold. The location of the sensor on the manifold allows for a shorter warm-up time for the sensor to reach operating temperature.



On vehicles that meet the requirements of the EURO III toxicity standards, a second oxygen concentration sensor is built into the exhaust system after the neutralizer.

Warning! The presence of lead and silicon compounds in the exhaust gases may cause the oxygen concentration sensor to fail. Therefore, the use of leaded gasoline is not allowed. When repairing the engine, do not use a sealant with a high silicone content (silicon compounds), vapors of which can enter the cylinders through the crankcase ventilation system and then into the exhaust tract. You should use a sealant that is specifically indicated on the packaging as being safe for the oxygen concentration sensor.

Coolant temperature sensor (DTOZH) - a semiconductor device - a thermistor, the electrical resistance of which changes with changes in the ambient temperature. DTOZH is installed in the thermostat housing. Based on the resistance of the sensor, the ECU evaluates the engine temperature mode. The obtained data are used to calculate most control commands for the elements of the engine management system, as well as to turn on the electric fan of the engine cooling system. If the DTOZH fails, the electronic control unit switches the system to backup mode.



Speed sensor the vehicle is mounted on the gearbox. The sensor operates on the Hall effect. The ECU calculates the vehicle speed based on the pulses generated by the sensor. The signal from the sensor also goes to the speedometer.



On the engine 21124 four are used ignition coils. They are installed directly on the spark plugs. This eliminates the reduction in spark power due to current leaks (this is possible when the insulation of high-voltage wires is damaged).



The 21114 engine has an ignition coil, which consists of two two-terminal ignition coils, made in a single housing. Spark formation occurs in two cylinders simultaneously (1-4 and 2-3). The ignition coil is connected to the spark plugs by high-voltage wires with non-removable tips.



Early model cars with 2111 engines and cars with 2112 engines were equipped with an ignition module (instead of ignition coil). The module also consists of dual two-terminal coils installed in a common housing. Additionally, the housing contains an integrated circuit that controls the operation of the coils.



On engines 2112 and 21124 aU17DVRM spark plugs are used, where:

• And the thread is M14x1.25;
• The hexagonal part of the body is under the key by 16 mm;
• 17 heat rating;
• D length of threaded part 19 mm, with flat seating surface;
• In the protrusion of the thermal cone of the insulator beyond the end of the threaded part of the housing;
• R built-in resistor;
• M bimetallic central electrode.

The engine can be equipped with spark plugs of similar type from different manufacturers (see table 16.2).



On engines 2111 and 21114 a17DVRM spark plugs are used, where:

• And the thread is M14x1.25;
• 17 heat rating;
• D length of threaded part 19 mm (with a flat landing surface);
• In the protrusion of the thermal cone of the insulator beyond the end of the threaded part of the housing;
• R built-in resistor;
• M bimetallic central electrode.

The engine can be equipped with spark plugs of similar type from different manufacturers (see table 16.2).

Nozzle - is an electromagnetic needle valve, on the outlet pipe of which a sprayer with four calibrated holes is made. The nozzle opens on the signal of the ECU, and the fuel under pressure is injected directly onto the intake valve. The amount of fuel entering the cylinder is regulated by the opening time of the nozzle. The engine has one nozzle per cylinder.



The purge valve of the adsorber is installed on the cover of the adsorber housing (for more details see. "Power supply system").

The diagnostic connector block is designed to connect an external diagnostic device (for example, DST-2M) to the engine management system. The block is installed on the instrument panel below on the driver's side.