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.