Principles of Operation
Interior Lighting
Principles of Operation
The interior lighting can be separated into 2 distinct modes of operation:
- Courtesy lighting
- Demand lighting
The Lighting Control Module (LCM) controls all of the interior lighting in the vehicle.
Lighting Control Module (LCM)
This vehicle uses an LCM to control lighting functions. The LCM is a microprocessor-based module that controls several vehicle subsystems, responds to electrical input signals from various switches, sensors, and external modules and is located on the LH side of the instrument panel. The LCM subsystem functions include:
- Headlamps with autolamps
- Turn signal lamps/hazard flasher lamps
- Cornering lamps
- Parking lamps
- Daytime Running Lamps (DRL)
- Fog lamps
- Courtesy lamps
- Demand lamps
- Battery saver
The LCM interfaces with the Driver Door Module (DDM) via the Standard Corporate Protocol (SCP) network for the illuminated entry feature.
The following lamps illuminate for courtesy lighting:
- Front footwell lamps
- Front map lamps
- Rear reading lamps
The following demand lamps are powered by the demand lighting output of the LCM:
- Glove compartment lamp
- Vanity mirror lamps
- Luggage compartment lamp
- Rear reading lamps
- Front map lamps
- Red/white map lamp (Police if equipped)
Each lamp has a dedicated switch that closes to ground to illuminate the lamp.
The front map lamps are powered by either the demand lighting circuit or the courtesy lighting circuit, depending upon the position of the switch associated with each lamp. When the customer turns the front map lamp switch on, the front map lamp is illuminated through power supplied by the LCM demand lighting circuit. If the customer moves the map lamp switch to the OFF position, the power from the LCM demand lighting circuit is interrupted and the lamp is reconnected to the courtesy lighting circuit.
The rear reading lamps are powered by either the courtesy lighting circuit or the demand lighting circuit.
The luggage compartment lamp is controlled by input from the trunk ajar switch, and is powered by the demand lighting output from the LCM.
The glove compartment lamp consists of a glove compartment lamp switch and wire and miniature bulb assembly. Opening the glove compartment door closes the switch which provides power to the glove compartment lamp switch and wire. The glove compartment lamp switch is grounded to the body sheet metal.
The vanity mirror lamp system consists of a switch and bulb assembly in the RH inside visor and the LH inside visor. Lifting the vanity mirror cover closes the vanity mirror lamp switch and provides power to the lamps.
The battery saver has the following inputs:
- Luggage compartment lid door ajar switch
- Ignition switch status
- Illuminated entry message
- Instrument panel dimmer switch
- Door ajar switch
- RKE transmitter
- Door unlock, luggage compartment door release
The battery saver has the following outputs:
- Courtesy lamps
- Demand lamps
When the ignition switch is turned to OFF, the courtesy lamps interrupt timer, and demand lamps interrupt timer begin their timeout. The interrupt timer is a feature of the LCM. Power is available to the courtesy lamps and demand lamps during timeout. At the end of the 10 (± 1) minute timeout period, the LCM disables power to the headlamps and courtesy lamps. At the end of the 30 minute timeout period, the LCM disables power to the demand lamps. If the instrument panel dimmer switch is causing the courtesy lamps to be on, then timeout is 30 minutes. Turning the ignition switch to ACC or RUN terminates the battery saver feature by disabling the interrupt timers and reinstating power to the lamps.
A reset event sets the courtesy lamps interrupt timer to zero. The reset events for the courtesy lamps and the demand lamps interrupt timer are as follows:
- Turning on the courtesy lamps using the instrument panel dimmer switch
- Opening any door (as detected by the door ajar switches)
- Luggage compartment lid ajar
- Any RKE transmitter button pressed
When the panic button is pressed on an RKE transmitter, the panic alarm overrides the courtesy lamps, demand lamps and headlamps battery saver functions for the necessary duration of the alarm.