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 MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 998 (LIGHTING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B257ACIRCUIT/SYSTEM TESTING
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2
Circuit/System Testing
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Circuit/System Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
DTC B257A
| Circuit | AUTO | PARK | HEAD |
|---|---|---|---|
| Headlamp Switch Headlamps Off Signal BCM Terminal 17 | Ground | Open | Open |
| Headlamp Switch Park Lamps Signal BCM Terminal 8 | Open | Ground | Ground |
| Headlamp Switch Headlamps On Signal BCM Terminal 12 | Open | Open | Ground |
- Ignition OFF, disconnect the BCM connector C2 and start with the headlamp switch in the AUTO position. Use the chart above to determine when and where a ground signal should be present. Test each connector circuit listed in the chart for the proper signal.
- If voltage is present on any circuit, test that circuit for a short to voltage.
- If the circuit/connections test normal, replace the headlamp and panel dimmer switch.
- If no ground signals are present, test the headlamp switch ground circuit for an open.
- If the circuit/connections test normal, replace the headlamp and panel dimmer switch.
- If all signal functions of the headlamp and panel dimmer switch circuits test normal, replace the BCM.
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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.