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Home >> Buick >> 2007 >> Lucerne CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 173 (Lighting Systems) >> Diagnostic Information and Procedures >> DTC B2645 >> Circuit Description

Circuit Description

WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.

The body control module (BCM) monitors the daytime running lamps (DRL) ambient light sensor signal circuit in order to determine if the DRL or the headlamps should be turned ON in the automatic lamp control (ALC) mode. When the BCM senses the ambient light sensor voltage is between 1-4.9 volts, either the DRL or the headlamps will be commanded ON.