Diagnostic Aids
- If the headlamps are manually turned ON when the headlamp relay coil supply voltage circuit is shorted to ground, the TBC fuse will open and the headlamp and panel dimmer switch can be damaged. When the TBC fuse opens, the scan tool will lose communication with the BCM.
- Perform a visual check for loose or poor connections at all related components.
- Refer to TESTING FOR INTERMITTENT & POOR CONNECTIONS .