1. Look for the fault light or MIL indicator light on the dashboard of the vehicle, and make sure that it is in the running state of the engine (usually it flashes several times after ignition and then goes out).

2. Connect the OBD diagnostic tool to the standard OBD2 interface of the car. If you don't have your own diagnostic tools, you can also send the car to the maintenance service station for diagnosis.

3. Start the diagnostic tool and select related options according to the menu prompts, such as scanning fault codes and reading fault codes.

4. The fault code information displayed on the tool screen determines the specific cause of vehicle fault and takes corresponding measures.