In order for the engine to work properly, the engine needs to start, which requires a starting line for the starter to work, the battery on the car needs to be charged, the engine has a generator, and the energy of the generator needs to be output through the wiring harness. Gasoline car also has the ignition system circuit, air conditioning compressor control circuit, the engine working state of the sensor circuit and so on. Therefore, the wiring harness of the engine is an essential part of the normal operation of the engine