Caution! Do not touch the ECU terminals with your hands: the engine control system is microprocessor-based, its electronic components can be damaged by electrostatic discharge.
Getting Started with Car Repairs (especially if the operations involve dismantling elements of the engine management system), remove the terminal from the negative battery terminal.
Warning! When the battery is disconnected from the vehicle's network, the fault codes will be deleted from the ECU memory. Therefore, before checking the engine management system using diagnostic equipment, (for example, DST-2M) do not remove the terminals from the battery terminals.
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.
Attention! 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) are not shorted to ground and 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.
Attention! 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 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 test lamp A 12-1.2-1 with a power of 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.
(The text is taken from the online resource: VazBook)
Attention! 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.