Circuit Description
WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The Body Control Module (BCM) uses the courtesy lamps supply voltage circuit as a input circuit and a output circuit. When used as an output circuit the BCM provides battery power to the courtesy lamps. When used as a input circuit the BCM provides an interface to the electrical loads which are controlled by the BCM when the output is inactive. This will allow for determination of the ON/OFF status of the loads.