The main wiring harness of the vehicle is generally divided into engines (ignition, EFI, power generation, start-up), instrumentation, lighting, air conditioning, auxiliary electrical appliances, etc. There are main wiring harness and branch wiring harness.

The main wiring harness of the vehicle often takes the instrument panel as the core part and extends forward and backward. It is divided into front wiring harness (including instrument, engine, headlight assembly, air conditioner, battery), rear wiring harness (rear lamp assembly, license plate light, luggage compartment light), canopy wiring harness (door, ceiling light, audio speaker), etc.