Courtesy Lamps Manual Operation
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 courtesy lamps, may be manually operated by the IP dimmer switch. When the IP dimmer switch is placed in the ON position the BCM receives a ground from the courtesy lamp switch signal circuit. Upon receiving the courtesy lamp switch signal the BCM then pulls low the courtesy lamp low control output circuit, which illuminates the courtesy lamps. The voltage for all interior lamps is supplied by the courtesy lamp supply voltage circuit of the BCM, whenever the BCM is active. The interior lamp switch will override any BCM operation of the interior lamps, such as entry illumination.