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 located on the instrument panel. The engine will then be able to continue operating (except in case of crankshaft position sensor failure), which allows you to get to the repair site under your own power. The ECU records the codes of detected faults in the random access memory (RAM).
To read the fault codes, an external diagnostic device, such as DST-2M, must be connected to the engine management system. For this purpose, the system has a diagnostic connector, the connector block of which is installed below the central console on the instrument panel. Access to the block is closed by a decorative cover.
You can read the fault codes at a service center that has the necessary equipment.
When servicing and repairing the engine management system, the following precautions must be taken:
- Do not touch the ECU terminals with your hands; the engine control system is microprocessor-based; the electronic components of the ECU may be damaged by electrostatic discharge.
- Getting Started with Car Repairs (especially if the operations involve dismantling elements of the engine control system), remove the terminal from the negative battery terminal.
When the battery is disconnected from the vehicle's network, the fault codes will be cleared from the ECU memory.
In many cases, to check the engine management system components, it is necessary to have power supply voltage in the electrical circuit of the system. In this case, disconnecting the wire blocks from the sensors and actuators of the engine management system is allowed only after the ignition is turned off.
You can disconnect the wiring harness connector from the ECU only after removing the terminal from the negative terminal of the battery.
If it is necessary to connect the battery to the vehicle's electrical system during repairs, first make sure that the disconnected wires (terminals of the pads, ends of the wires) do not short to ground and that the ignition is off. First connect the terminal to the positive terminal of the battery, then to the negative. Turn on the ignition only for the duration of the measurements.
The engine management system uses electronic components with a supply voltage of 5 V. They are supplied with voltage from the vehicle's electrical network (voltage in which is more than 12 V) will result in failure of the engine management system.
To check the engine management system, use a multimeter, the internal resistance of the device in the voltmeter mode should be at least 10 MOhm. If necessary, to check the power supply circuits under 12 V, you can use a test lamp, but the lamp power should be less than 4 W (the instrument cluster control lamp A 12-1.2-1, power 1.2 W or the cigarette lighter backlight lamp AMN 12-3-1 - 3 W will do).
Before starting the engine, make sure the terminals are securely connected to the battery posts.
To avoid damage to the electronic components of the ECU, do not disconnect the wire terminals from the battery terminals while the engine is running.
[The article is taken from the website VAZbook.ru]
Note: Checking the condition of the engine management system components is shown below in the relevant sections of the chapter "Engine Management System".