Materials:
* Multimeter
* Insulated wires for jumpers (if necessary)
* Electrical tape (if necessary)
* Diagnostic scanner (optional)
Steps:
1. Preparation
* Provide access to the vehicle’s electrical system.
* Turn off the engine and wait until all systems have cooled down.
* Disconnect the negative battery terminal for safety.
2. Battery check
* Set the multimeter to measure direct current (DC) voltage.
*Connect the red wire to the positive terminal of the battery and the black wire to the negative terminal.
* The voltage should be between 12.6 and 12.8 V. If it is below 12.2 V, the battery needs to be charged or replaced.
3. Check the charging system
* Start the engine.
* Set the multimeter to measure direct current (DC) voltage.
*Connect the red wire to the positive terminal of the battery and the black wire to the negative terminal.
*Voltage should be between 13.5 and 14.5 V. If it is too low or too high, there may be a problem with the alternator, voltage regulator, or wiring.
4. Checking the starter
* Set the multimeter to measure direct current (DC) voltage.
* Remove the positive cable from the starter terminal.
*Connect the red wire to the starter terminal and the black wire to the cable.
* Have an assistant turn the key to the start position.
* During startup, the voltage should be around 10-12V.
5. Wiring check
* Set the multimeter to measure resistance (ohms).
* Disconnect connectors from components (eg lamps, fuses, relays).
* Connect the red and black wires to the connector pins.
* Resistance should be close to zero (no more than 1-2 Ohms). If the resistance is higher, there may be a wiring problem.
6. Checking fuses
* Remove fuses from the fuse box.
* Inspect fuses for burnt wires.
* Replace blown fuses with new ones of the same rating.
7. Relay check
* Remove the relay from the relay block.
* Check the number of contacts on the relay.
* Set the multimeter to measure resistance (ohms).
* Connect the red and black wires to the relay contacts according to the number of contacts.
*Measure the resistance between different pins.
* Resistance values must comply with manufacturer specifications.
8. Checking lamps
* Turn on your headlights, hazard lights and other lights.
* Inspect lamps for burnout or damage.
* Replace burnt out or damaged lamps with new ones.
9. Using a diagnostic scanner (optional)
* Connect the diagnostic scanner to the vehicle’s OBD-II port.
* Turn on the ignition, but do not start the engine.
* Run diagnostics and read fault codes.
* Decipher fault codes and fix any problems found.
10. Completion
* Connect the negative terminal of the battery and tighten it.
* Reinstall all connectors, fuses, relays and lamps.
* Check all electrical systems for proper operation.