DTC B2648: AMBIENT LIGHT SENSOR CIRCUIT HIGH GMC Envoy I

TBC module monitors circuit No. 278 (White wire) to determine when headlights need to be turned on when headlight switch is in AUTO mode. See WIRING DIAGRAMS . When circuit to TBC module is shorted to battery voltage, DTC will set.

Conditions for setting DTC

1. Circuit No. 278 (White wire) is shorted to battery voltage.
2. System voltage 9-16 volts.
3. Conditions met for .5 second.