When replacing or troubleshooting a fuel pump on a GM vehicle, understanding the fuel pump wiring color codes is essential. Whether you're working on a Silverado, Tahoe, Suburban, or any other GM model, the wire colors tend to follow a consistent pattern — but you should always verify for your specific model.
This guide explains the standard GM fuel pump wire color codes, their functions, and helpful tips for repair or replacement.
gm fuel pump wires color codes
🔌 Standard GM Fuel Pump Wiring Color Code
| Wire Color | Function | Typical Location |
|---|---|---|
| Grey (Gray) | Fuel pump positive (12V power) | From fuel pump relay or PCM |
| Black | Ground for fuel pump | Chassis or frame ground |
| Purple | Fuel level sensor signal | To fuel gauge on dash |
| Black with White Stripe | Ground for fuel level sensor | Shared or separate ground circuit |
🔍 Wire Function Breakdown
🔸 Gray Wire – Fuel Pump Power
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Function: Supplies 12V+ to run the fuel pump.
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Activated by: Fuel pump relay (via ECM or ignition).
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Tip: Check for voltage here when ignition is ON for diagnostics.
🔸 Black Wire – Fuel Pump Ground
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Function: Provides the ground connection for the fuel pump.
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Location: Usually grounded to the frame or near the rear harness.
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Tip: Poor grounding can lead to pump failure or low pressure.
🔸 Purple Wire – Fuel Level Sending Unit
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Function: Carries the signal from the fuel level float to the dashboard gauge.
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Voltage Range: Typically 0.5V to 5V depending on fuel level.
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Tip: Erratic fuel gauge? This wire may be corroded or broken.
🔸 Black/White Wire – Fuel Sender Ground
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Function: Ground for the fuel level sender circuit.
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Shared?: Sometimes shares ground with the pump or may be separate.
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Tip: Ensure a clean ground here for accurate fuel readings.
⚙️ GM Fuel Pump Wiring Diagram (Basic Concept)
🧪 Testing Tips for GM Fuel Pump Wiring
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✅ No pump activity? Check for 12V on the gray wire with ignition ON.
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🔍 Weak pump or no prime? Confirm the black ground wire has solid continuity to chassis ground.
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📏 Inaccurate fuel gauge? Test purple wire voltage vs. actual fuel level.
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⚠️ Fuse check: Look for “ECM B” or “Fuel Pump” fuses in the underhood fuse box.
🔧 Where You’ll Find These Wires
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Inside the fuel tank harness going to the pump/sender module.
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In the underbody wire loom near the rear axle.
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At the fuel pump relay/fuse center, often under the hood.
🚘 Models Where This Applies
These wire color codes are commonly found in:
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Chevrolet Silverado, Tahoe, Suburban
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GMC Sierra, Yukon
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Chevrolet Impala, Malibu
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Buick Regal, LaCrosse
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Pontiac Grand Prix
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And most other GM models from late 90s to mid-2010s
(Always check your vehicle-specific wiring diagram to be sure.)
🔚 Conclusion
Understanding the GM fuel pump wire color code helps with faster diagnostics, safer installations, and reliable performance. While GM wiring is relatively standardized, minor differences may exist between models and years — always verify with a multimeter or wiring diagram before making connections.
