DTC B2647: AMBIENT LIGHT SENSOR CIRCUIT LOW 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 low, DTC will set.

Conditions for setting DTC

1. Circuit No. 278 (White wire) is shorted to ground or open, or circuit No. 750 (Gray wire) is open.
2. System voltage 9-16 volts.
3. Conditions met for .5 second.