22
2026-06
Colors of Automotive Wiring Harnesses and Their Functions
Main power wire/positive terminal. Typically connected to the battery’s positive terminal or a constant‑power source, providing a +12 V supply for basic power functions, such as the input terminals of the fuse box and memory‑retention circuits.
Red (R): Main power wire/positive terminal. Typically connected to the battery’s positive terminal or a constant‑on power source, providing a +12 V supply for basic power needs, such as the input terminals of fuse boxes and memory‑retention circuits.
Black (B): Ground wire/negative terminal. A standardized grounding wire that connects to the vehicle’s metal body structure to form a circuit; on some models, white or brown is also used for grounding.
Yellow (Y): Ignition switch control circuit (IGN). It is energized only when the ignition switch is in the ON/START position and supplies power to engine control systems, the instrument panel, and other components that require ignition to operate.
Blue (Bi/L): Signal or special control. Commonly used for high-beam headlights, air-conditioning compressor control, or sensor signal transmission, depending on the vehicle model.
Green (G): Lighting signal system. Commonly used in the control circuits of turn signals, brake lights, and tail lights to transmit lighting‑action signals.
Brown (Br): Auxiliary power or tail light. In European vehicle series, it is often used for grounding or supplying power to the tail lights; in some models, it is employed for internal radiator or temperature‑control devices.
White (W): Auxiliary signal or ground wire. Often used as a sensor signal line or auxiliary circuit; in some American‑made vehicles, it serves as the ground reference.
Purple (V): Reverse or audio/video system. Commonly used for reverse lights, reverse‑camera power supply, or high‑end audio‑multimedia signal lines.
Orange (O): Warning or high voltage. In low-voltage systems, it is used for seatbelt warning and malfunction indicator lights; in hybrid and electric vehicles, the thick orange wire denotes high-voltage (HV) electricity and must never be touched with bare hands.
Gray (GR): Sensor communication. Commonly used for transmitting signals from sensors such as throttle position and coolant temperature, or for wiring in in-vehicle and external communication modules.
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