Principles of Operation

PRINCIPLES OF OPERATION

Interior Lighting System
The instrument cluster (IC) illuminates the interior lamps based on input signals from the door ajar switches, headlamp switch and the vehicle security module (VSM). The IC monitors the door ajar switch status on the input circuits for a ground supplied through the ajar switches indicating an open door. The IC then grounds the battery saver relay and the interior lamp relay control circuits in order to energize the battery saver relay and the interior lamp relay. When the relays are energized, voltage is supplied to the interior lamp circuits.

Illuminated Entry
Illuminated entry is activated when the remote keyless entry (RKE) transmitter provides a signal to the VSM. The VSM provides a signal to alert the IC to illuminate the interior lamps. The interior lamps remain illuminated for a period of up to 25 seconds after all doors are closed or until the ignition is switched from the OFF position.

Demand Lighting
The battery saver relay provides power to the demand lamps. The demand lamp switch, which when activated, provides power to the selected demand lamp. The battery saver relay is energized anytime the IC is not in sleep mode.

Battery Saver
The IC provides a ground circuit for the battery saver relay coil. The battery saver relay provides power to the demand lamps. When the ignition switch is switched to the OFF position the battery saver relay remains energized until a predetermined time-out has elapsed and the IC deactivates the battery saver relay.

Field-Effect Transistor (FET) Protection
The IC utilizes a FET protective circuit strategy for some of its outputs. Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down (turns off the ground provided by the module) when a fault is detected. A continuous DTC is stored at the time of the fault. When an excessive circuit load occurs several times, the module shuts down the output until a repair procedure is carried out. At the same time, the continuous DTC that was stored on the first failure cannot be cleared by a command to clear the continuous DTCs. The module does not allow this code to be cleared or the circuit restored to normal until a successful on-demand self-test proves that the fault has been repaired. After the on-demand self-test has successfully completed (no on-demand DTCs present), the continuous DTC clears and the circuit function returns.

The IC FET protected output circuits for the instrument panel illumination system are for the courtesy lighting and battery saver output circuits.