DTC B2647: Ambient Light Sensor Circuit Low: Notes
WARNING: This page is about a different car, the 1999 GMC Sierra and 1999 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
BCM monitors circuit No. 278 (White wire) to determine if Daytime Running Lights (DRL) or Auto Headlights (AHL) should be turned on when headlight switch is in AUTO mode. When BCM senses ambient light sensor voltage between 1.7-4.7 volts, (light state) DRL will be commanded on. When BCM senses ambient light sensor voltage between 0.2-1.0 volt, (dark state) AHL will be commanded on.
Conditions for setting DTC:
- Circuit No. 278 (White wire) is shorted to ground or open when ambient light sensor input voltage is less than 0.2 volt.
- System voltage 9-16 volts.
- Conditions met for .5 second.