Interior Lamps Dimming

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.

The second interior lighting group includes lamps which may be dimmed. This group may use a combination of vacuum fluorescent (VF) illumination, LED illumination and incandescent lamps.

Headlamp switch
Hazard switch
Ashtray lamp
HVAC control module
Driver information center (DIC)
Clock
Radio
Rear door window switches
Traction control switch
Floor shifter assembly
Garage door opener transmitter
Sunroof switch
Sunshade switch
Rear seat heated seat switches
Rear seat lumbar switches
Middle door window switches (w/V4U)
Auxiliary HVAC control module (w/CJ4)
Steering wheel controls

When the ignition switch is turned to the RUN position, the instrument panel cluster (IPC), radio VF display, and the HVAC control assembly turns ON at maximum brightness. When the headlamp switch is in the PARK or HEADLAMP ON position, all incandescent and LED back lighting turn ON at the dimming level indicated by the instrument panel (I/P) dimmer switch. The dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The 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 I/P lamps supply voltage circuit and the LED dimming supply circuit to all related interior lamps, illuminating them to the desired level of brightness. At the same time the BCM also sends a GMLAN serial data message to the driver door module (DDM) and the front passenger door module (FPDM) indicating the back lighting request with the desired level of brightness. The door modules then illuminate the door switches and the heated/cooled seat switch back lighting to the requested intensity.