Circuit/System Description
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) supplies a voltage reference through the I/P dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the interior lamp switch. When the dimmer switch is placed in a desired brightness position, reference voltage is applied through the dimmer switch rheostat and the I/P dimming signal circuit to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage through the instrument panel lamp supply voltage circuit to the lamps. At the same time the BCM sends a serial data message requesting the front door modules to illuminate the door switches.