Principles of Operation

PRINCIPLES OF OPERATION

Dimmable Backlighting
The lighting control module (LCM) generates a variable pulse width modulated (PWM) voltage which is distributed to the dimmable components when the headlamp switch is in the PARKING LAMPS or HEADLAMPS ON positions. Light intensity is adjusted by rotating the instrument panel dimmer switch. The dimmable backlighting components consist of:
- Adjustable pedal switch
- Audio unit
- Audio/navigation control unit (if equipped)
- Traction control switch
- Headlamp switch
- Message center
- Rear audio/climate control module
- Clock
- Front cigar lighter
- RH rear cigar lighter
- LH rear cigar lighter
- Steering wheel speed control switches
- Steering wheel audio/climate control switches

The LCM communicates backlighting intensity signals on the standard corporate protocol (SCP) network to the following:
- Dual automatic temperature control (DATC) module
- Overhead console
- Instrument cluster

If the headlamps are operated during daylight hours, the light sensor amplifier detects high ambient light levels and signals the LCM to keep illumination levels readable and therefore are non-adjustable on the following components:
- Audio unit
- DATC unit

When the headlamp switch is in the OFF position, the instrument cluster internally powers the gauge illumination lamps to full brightness.

Fixed Level Backlighting
The following components have fixed level backlighting that is illuminated when the ignition switch is in the RUN or ACCESSORY position:
- Exterior mirror control switch
- Heated seat switches
- Driver window control switch
- Passenger window control switch
- RH rear window control switch
- LH rear window control switch
- Driver door lock control switch
- Passenger door lock control switch