Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1506 (WIRING SYSTEMS AND POWER MANAGEMENT - SERVICE, TROUBLESHOOTING & DIAGNOSIS)POWER MODE MISMATCHCIRCUIT/SYSTEM VERIFICATION
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6
Circuit/System Verification
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Verification
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
- Verify that the following DTCs are not set: U1814, B1428.
- If either of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- With a scan tool, access BCM, Power Mode data display list and compare all parameters listed with the corresponding ignition key position. The PMM Power Mode Parameters table below illustrates the correct state of these input parameters in correspondence to the ignition switch position. The circuits which the individual parameters are related to are in parentheses.
PMM Power Mode Parameters
| Ignition Switch Position | Current Power Mode | Ign. Off/Run/Crank (Terminal 5) |
Ignition Accessory/Run (Terminal 3) |
Ignition Run/Crank (Terminal 2) |
|---|---|---|---|---|
| Off Key Out | Off | Key Out/ACC | Inactive | Inactive |
| Off Key IN | Off | Key In/Off | Inactive | Inactive |
| Accessory | Accessory | Key Out/ACC | Active | Inactive |
| Run | Run | Run | Active | Active |
| Start | Crank Request | Crank | Inactive | Active |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.