The wiring harness is the central nervous system of the vehicle, an organized web of insulated wires, terminals, and connectors that transmit information and energy. It connects the engine, transmission, sensors, and interior electronics to the central computer (ECU) and power sources. Unlike loose wires, a harness is bound together by durable tape, conduit, or woven sleeves to protect against heat, vibration, and abrasion. Damage to the harness is often difficult to diagnose and can lead to intermittent electrical gremlins or total system failure.