The ECU receives the following information:
- position and frequency of rotation of the crankshaft;
- the position of the camshafts;
- mass air consumption by the engine;
- coolant temperature;
- intake air temperature;
- throttle position;
- oxygen content in the exhaust gases;
- the presence of detonation in the engine;
- amplitude of vibrations of the car body;
- vehicle speed;
- voltage in the vehicle's on-board network;
- request to turn on the air conditioner (on cars in the variant).
Based on the information received, the ECU controls the following systems and devices:
- fuel supply (injectors and electric fuel pump);
- ignition system;
- idle control;
- an adsorber of system of catching of vapors of gasoline;
- engine cooling fan;
- air conditioning compressor clutch (on cars in the variant);
- diagnostic system.
ECU turns on output circuits (injectors, various relays, etc.) by closing them «mass» through its output transistors. The only exception is the relay circuit of the electric fuel pump, which is powered through a power relay. In turn, the relay winding is controlled by the ECU by closing one of the outputs to «mass».
The ECU is equipped with a built-in diagnostic system. It can recognize ECM malfunctions, warning the driver about them through a warning light «CHECK ENGINE». In addition, the ECU stores diagnostic codes that indicate the malfunction of a particular element of the system and the nature of this malfunction in order to assist specialists in diagnosing and repairing.
The ECU contains the following types of memory:
- programmable read only memory (PROM);
- random access memory (RAM);
- electrically reprogrammable memory (ERPZU).
Programmable Read Only Memory (PROM)
It contains a general program, which contains a sequence of working commands (control algorithms) and various calibration information. This information is injection, ignition, idle control data, etc., which depend on vehicle weight, engine type and power, transmission ratio, and other factors. PROM is also called a calibration memory. The contents of the PROM cannot be changed after programming. This memory does not need power to save the information recorded in it, which is not erased when the power is turned off, i.e. this memory is non-volatile.
Random access memory (RAM)
This «notebook» ECU. The controller's microprocessor uses it to temporarily store the measured parameters it uses for calculations and intermediate information. The microprocessor can enter data into it or read them out as necessary.
The RAM chip is mounted on the controller PCB. This memory is volatile and requires an uninterruptible power supply to maintain. When the power supply is interrupted, the diagnostic trouble codes and calculated data contained in the RAM are erased.
Electrically reprogrammable memory (ERPZU)
Used for temporary storage of car anti-theft system passwords (immobilizer). The password codes received by the ECU from the immobilizer control unit are compared with the codes stored in the EEPROM, as a result of which the engine start is allowed or prohibited.
The EEPROM records vehicle operating parameters such as total vehicle mileage, total fuel consumption, and engine operating time.
ERPZU also registers some violations of the engine and car:
- operating time of the engine with overheating;
- engine operation time on low-octane fuel;
- engine operation time exceeding the maximum allowable speed;
- engine operation time with misfiring of the air-fuel mixture, the presence of which is indicated by the signal lamp of the engine management system;
- engine operation time with a faulty knock sensor;
- engine operation time with a faulty oxygen concentration sensor;
- the time of movement of the car with excess of the maximum permitted speed during the break-in period;
- vehicle movement time with a faulty speed sensor;
- number of battery disconnections with the ignition switch on.
EEPROM is non-volatile, it can store information without powering the controller.
The ECU is located under the instrument panel console.
To replace the electronic control unit, you will need a Phillips screwdriver.
1. Disconnect the wire from the terminal «minus» battery.
2. Remove the right lining of the floor tunnel (see «Removal and installation of floor tunnel linings»).
3. Grasp the two tabs and pull out the fixing bracket along the connector plane until it stops.
4. Disconnect the block with wires from the computer.
5. Unscrew (not completely) two nuts securing the ECU bracket.
Note. On the opposite side, the ECU bracket is not secured with a nut.
6. Move the bracket with the computer to the right and, lifting it up a little, remove the computer from the car.
7. Install the computer in the reverse order of removal.
Attention! A defective electronic unit can only be replaced with a new unit in which the anti-theft function is not activated. With such a replacement, the ECU will allow the engine to be started regardless of the immobilizer. To activate the anti-theft function, perform the immobilizer learning procedure.
To activate the anti-theft function of the new controller, you must complete the learning procedure (see «Learning immobilizer keys»), using the available training and working keys.