Circuit/System Testing
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. 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.