Understanding the GM wire harness color code is crucial for anyone working on Chevrolet, Buick, Cadillac, or GMC vehicles. Whether you're troubleshooting electrical issues, installing aftermarket components, or restoring classic cars, knowing how to read and apply GM's wire color coding can save time, prevent errors, and ensure safe, reliable electrical work.
gm wire harness color code
📘 Overview of GM Wire Color Coding System
Since the 1970s, General Motors has maintained a fairly consistent wire color coding system across most of its vehicles. This system includes solid-colored wires and striped wires, where the base color indicates the main function and the stripe provides further detail.
🔹 Solid Colors
Used for primary functions such as power, ground, or lighting.
🔹 Striped Colors
Combinations used for more specific signal routing or identification.
Note: Always confirm wire functions using wiring diagrams and testing tools, especially for newer models with more complex systems.
🔌 GM Standard Wire Color Codes and Functions
🔋 Power and Ground
| Color | Function |
|---|---|
| Red | Battery power, main 12V circuits |
| Orange | Constant power (radio memory, clock, security) |
| Black | Ground, chassis or engine negative |
🔑 Ignition and Engine Management
| Color | Function |
| Pink | Ignition switched power, accessory feeds |
| Yellow | Ignition coil power, ECU power, starter signal |
| Brown | Starter relay, ignition switch start position |
💡 Lighting Circuits
| Color | Function |
| White | Headlights, fog lights, high beam |
| Gray | Parking lights, tail lights, license plate |
| Green | Turn signals, brake lights, hazard flashers |
| Blue | Dimmer switch, dash lights, low/high beam control |
❄ HVAC and Comfort
| Color | Function |
| Purple | A/C circuits, blower motor, compressor clutch |
| Tan/Beige | Heater fan, ventilation, recirculation |
🎵 Audio and Electronics
| Color | Function |
| Dark Blue | Antenna control, speaker (-), amp ground |
| Light Blue | Speaker (+), amp power, signal circuits |
🎯 Common GM Striped Wire Combinations
| Color Combination | Function |
| Red/Black | Switched power, accessory circuits |
| Black/White | Switched ground, sensor ground |
| Yellow/Black | ECM circuits, ignition timing |
| Green/White | Turn signal returns, flasher ground |
| Blue/White | Headlight control, DRL systems |
🚗 Vehicle-Specific Applications
Chevrolet: Camaro, Silverado, Tahoe
- Trailer wiring: Standard 7-pin colors
- 4WD systems: Unique circuit colors
- Track/sport packages: Extra circuits, special codes
Cadillac
- Premium Bose systems: Proprietary wire colors
- HUD, infotainment, ADAS: Specialized wiring
GMC
- Commercial trucks: PTO, fleet lighting, upfitter circuits
📅 Color Code Changes by Vehicle Era
1970s–1980s (Classic)
- Simpler systems, basic color usage
- Ideal for restorations and rebuilds
1990s–2000s (Transition)
- OBD-II compliance
- ECM/fuel injection wiring added
2010s–Present (Modern)
- CAN Bus and advanced electronics
- Infotainment, hybrid/EV, ADAS wiring
🧪 Troubleshooting by Wire Color
Power Issues
- Red: Battery voltage?
- Black: Good chassis ground?
- Orange: Constant 12V?
- Pink: Switched with ignition?
Lighting Issues
- White: Headlights
- Gray: Tail/parking lights
- Green: Turn signals
- Blue: Dimming/multifunction switch
🔧 Aftermarket Installations
Stereo Wiring
| Function | GM Color | ISO Color |
| Switched 12V | Pink | Red |
| Constant 12V | Orange | Yellow |
| Ground | Black | Black |
| Remote/Ant Power | Blue | Blue |
| Speakers (LF, RF, LR, RR) | White, Gray, Green, Purple | Match by polarity |
Alarms & Trailer Wiring
- Pink: Accessory feed
- Brown: Starter disable or relay
- Green/White: Signal input
- 7-pin trailer: Follows standard (white=ground, green=RT, yellow=LT, etc.)
🛠 Tools & Resources
Testing Tools
- Digital Multimeter
- Test Light
- Wire Stripper & Crimper
- Circuit Tester
Documentation
- GM Factory Service Manuals
- Mitchell, ALLDATA
- Wiring diagrams
- Online color charts
⚠ Safety and Best Practices
- Always disconnect the negative battery terminal before working.
- Use proper fuse ratings and wire gauges.
- Label wires and take photos of connections.
- Verify all functions before final assembly.
📚 Advanced Use Cases
Performance Mods
- ECM pinouts, sensor colors
- Fuel system wiring
- Ignition upgrades
Restoration
- Use correct NOS or reproduction harnesses
- Factor in color fading and original documentation
✅ Conclusion
Mastering the GM wire harness color code is invaluable for technicians, restorers, and DIYers alike. While GM maintains general consistency, always double-check with model-specific diagrams and real-time testing. Doing so ensures safety, efficiency, and successful outcomes in every electrical project.
Whether you’re wiring up a sound system, fixing a light, or restoring a classic muscle car, let this guide be your go-to reference for understanding GM electrical systems.
