Detecting automotive circuit faults requires a systematic investigation combining multiple methods. First, conduct a visual inspection to check for loose wire harness connectors, ablated wire insulation, or obviously damaged components-for example, corroded battery terminals should be addressed immediately. Use the continuity test mode of a multimeter to measure circuit connectivity; if the resistance value deviates from the standard by more than 10%, focus on troubleshooting. Simultaneously, measure the voltage (the alternator output should be 13.8-14.5V, and the voltage from the battery positive terminal to the vehicle chassis should exceed 12.4V). The test light method can quickly verify power supply and grounding status: connect the test light to the circuit test point, and illumination indicates proper power supply. For complex faults, connect the manufacturer's diagnostic tool to read fault codes, analyze Pxxxx codes to locate the issue, or use an oscilloscope to detect sensor waveform distortion. The short-circuit method and open-circuit method are used to verify open or short circuits respectively, but avoid directly shorting the power supply during operation. In practice, perform static testing first followed by powered verification, adhering to the "simple before complex" principle-for instance, check fuses before investigating module power circuits. These methods can efficiently diagnose problems ranging from simple wire breaks to ECU control module failures.
