Circuit/System Description

WARNING: This page is about a different car, the 2011 Cadillac DTS. 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 instrument panel (I/P) dimming voltage reference circuit to the interior lamp dimmer switch, which is part of the headlamp 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 lamps dimmer switch 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 and the backlight lamp control circuit illuminating the lamps on these dimming circuits. At the same time the BCM sends a serial data message requesting the front door modules to illuminate the door switches. For more detailed information concerning interior lamp operation refer to Interior Lighting Systems Description and Operation .