DTC B2648: Ambient Light Sensor Circuit High: 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 Automatic 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 battery voltage.
- System voltage 9-16 volts.
- Conditions met for .5 second.