Automobile main wiring harness is generally divided into engine (ignition, EFI, power generation, starting), instrumentation, lighting, air conditioning, auxiliary electrical appliances and other parts, there are main wiring harness and branch wiring harness. A main harness has many branch harnesses, just like a tree pole and branches. The main harness of the vehicle usually takes the dashboard as the core part and extends back and forth. Because of the length relationship or the convenience of assembly, some automobile wiring harnesses are divided into front wiring harnesses (including instrument, engine, headlight assembly, air conditioning, battery), rear wiring harnesses (taillight assembly, license plate lamp, suitcase lamp), top wiring harnesses (door, ceiling lamp, sound horn) and so on.