Principles Of Operation

Interior Lighting

Principles of Operation

The Body Control Module (BCM) supplies voltage (and ground for the courtesy lamps) to the interior lighting system. The interior lighting system illuminates the courtesy lamps to enhance visibility of the interior when a vehicle door is ajar. The BCM controls all interior lighting functions and timing by monitoring inputs from the door ajar switches, luggage compartment lid/liftgate ajar switch, door lock switch, input from the Remote Keyless Entry (RKE) system and the ignition state.

The voltage supply circuit to the BCM for the interior lamps is also used for the horn.

Ambient Lighting

The ambient lighting module provides voltage and ground to the LEDs. The ambient lighting switch is an input to the ambient lighting module. With each press of the ambient lighting switch, the ambient lighting module cycles through a different color variation or turns the ambient lighting feature off. There are 3 different color (red, blue and green) LEDs housed within each LED assembly. By illuminating various color combinations, the LEDs are able to produce 7 different colors of ambient light. The module retains the last color setting between ignition cycles.

Field-Effect Transistor (FET) Protection

A FET is a type of transistor that, when used with module software, monitors and controls current flow on module outputs. The FET protection strategy prevents module damage in the event of excessive current flow.

The BCM utilizes a FET protective circuit strategy for many of its outputs (such as a turn lamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down when a fault event is detected. A short circuit DTC sets when the fault event occurs.

The circuit remains off until the fault is corrected and the ignition is cycled off and then back on, the module resets the FET protection and allows the circuit to function.

The FET protected circuits for the interior lighting system are the interior lamp voltage supply, courtesy lamp ground and ambient lighting module voltage supply circuits.