Common faults of automobile lines include poor contact of connectors, short circuit between wires, open circuit, grounding, etc. The causes are as follows: 1) The natural damage of the wire harness exceeds the service life, which causes the aging of the wire, the rupture of the insulation layer, and the significant decline of the mechanical strength, resulting in short circuit, open circuit, grounding, etc. between the wires, resulting in the burning of the wire harness. 2) Damage to wire harness caused by electrical equipment failure When electrical equipment has overload, short circuit, grounding and other faults, it may cause damage to wire harness. 3) When assembling or repairing auto parts by human fault, the wire harness is damaged by metal objects, which will break the insulation layer of the wire harness; The positive and negative leads of the battery are connected reversely; When repairing circuit faults, random connection and random cutting of wire harness and wires can cause abnormal operation of electrical equipment. Fig. 3 Harness