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 Repair (especially if the operations are related to the dismantling of elements of the engine control system), disconnect the terminal from the negative battery terminal.
When the battery is disconnected from the vehicle's network, fault codes will be deleted from the computer's memory.
In many cases, to check the elements of the engine control system, it is necessary to have a supply voltage in the electrical circuit of the system. At the same time, it is allowed to disconnect the wire blocks of the senders and the actuating elements of the engine control system only after the ignition is turned off.
Disconnect the wiring harness block from the computer only after removing the terminal from the negative battery terminal.
If it is necessary to connect the battery to the car's electrical network during repairs, first make sure that the disconnected wires (terminal blocks, wire ends) do not close on «mass» and that the ignition is off. Connect the battery positive terminal first and then the negative terminal. Switch on the ignition only for the duration of the measurements.
The engine management system uses electronic components, the supply voltage of which is 5 V. Supplying voltage to them from the vehicle's electrical network (voltage in which more than 12 V) will damage the engine control system.
To check the engine management system, use a multimeter; the internal resistance of the device in voltmeter mode must be at least 10 MΩ. If necessary, a test lamp can be used to check power circuits that are energized at 12 V, but the lamp power must be 3 W (suitable lamp A 12-1.2-1 power 1.2 W).
Before starting the engine, make sure that the terminals are securely fastened to the battery terminals.
To avoid failure of the electronic components of the computer, it is impossible to disconnect the wire terminals from the battery terminals while the engine is running.
If the engine control system is inoperable, check the condition of the fuses (see «Fuse and relay box»). If a blown fuse is found, it must be replaced. If the fuse blows again, check the power circuit, find and fix the problem (see below, «Checking the technical condition of the engine management system» and see «Electrical equipment - checking the technical condition»).
Recommendations
When checking the elements of the control system, there is a need to connect the multimeter to the terminals of the connecting blocks, sensors and other parts of electrical equipment. To connect to insulated terminals, use probes with fine tips or use pieces of copper wire. You should not forcefully stick the probes into the terminals, since subsequently poor electrical contact is possible in such connectors, causing interruptions in the operation of the engine control system. For connection to non-insulated terminals of connection blocks (plugs) you can use segments of thin PVC tubes. If you put them on the leads and insert the ends of the multimeter probes into them, then they will hold the probes (ensuring reliable contact with the terminals) and at the same time isolate their ends from short circuit.
To check the voltage drop in the circuit sections, you need to connect a voltmeter without disconnecting the wire blocks. This kind of measurement can be performed using a sewing needle with a copper wire wound around its end (for connecting the voltmeter probe).
For convenience, you can solder the copper strands of the insulated wire to the needle. The needle is pierced in the wire insulation of the circuit under test and measurements are taken.