A systematic approach is required to troubleshoot automotive electrical faults. First, conduct a visual inspection to check for loose wire harness connectors, ablated wire insulation, or visibly damaged electrical components. Corrosion on battery terminals should be addressed promptly. If the resistance deviation exceeds 10%, further investigation is needed. Voltage testing should be performed with the ignition switch on; the normal voltage at the generator output terminal should be 13.8-14.5V, and the battery voltage should remain above 12.4V. It is best to connect a 10A fuse in series during measurement to protect the instrument. A diagnostic tool can read fault codes to quickly locate electronic control system issues, with priority given to Pxxxx-series electrical fault codes. In practice, it is advisable to follow the principle of static testing before dynamic testing: complete basic detection after power-off, then verify after power-on. For poor contact issues, the voltage drop test method can be used to measure the voltage difference at the connector. The test light method is suitable for quickly determining power and ground status, while the replacement method is applicable to intermittent faults that are difficult to locate-replace the suspected faulty component with a known-good one for verification. Notably, special attention should be paid to the continuity of the ECU main power supply line during modern vehicle electrical maintenance; an abnormality in this circuit can cause complete electrical system failure. During testing, always disconnect the negative battery terminal first to prevent short circuits.
