Lamps/Lighting - Interior (Service Information): Operation

Most lamps of the interior lighting system can be divided into two general classifications based upon the circuit that controls their operation: The courtesy lamp circuit, or the panel lamps dimmer circuit. The exception is the glove box lamp, which has a unique dedicated circuit. Following are paragraphs that briefly describe the operation of each of these interior lighting circuits.

• Courtesy Lamp Circuit  - The courtesy lamp circuit includes the cargo/dome lamps located on the roof supports or in the headliner. The lamps in the courtesy lamp circuit are provided with battery voltage and ground by the Body Control Module (BCM) using internal low-side drivers through two ground circuits based upon hard-wired inputs from the ignition switch and the door ajar switches. The BCM also uses electronic message inputs received from other electronic modules in the vehicle over the Controller Area Network (CAN) data bus to control these outputs.

  When a door ajar switch input to the BCM transitions to closed, the BCM will illuminate the courtesy lamps and keep them active for up to about 3 minutes. After all of the ajar switch inputs transition to open, the BCM will keep the courtesy lamps illuminated for about 10 seconds. The BCM also provides courtesy lamp operation based upon certain inputs received from the Remote Keyless Entry (RKE) transmitter to provide an Illuminated Entry feature and in response to certain electronic message inputs received from the Occupant Restraint Controller (ORC) or the Powertrain Control Module (PCM) over the CAN data bus.

  For those lamps in the courtesy lamp circuit with independent switching such as the dome/reading lamps, the BCM provides a second feed to the switches using another internal low-side driver through a separate load shed circuit. The BCM provides a battery saver (load shedding) feature for these lamps, which will automatically turn the lamps OFF if they are left ON for more than about fifteen minutes with the ignition switch in the OFF position.

• Panel Lamp Dimmer Circuit  - The non-dimming panel lamps includes several circuits. These circuits control the backlighting of the HVAC controls, the window controls, the upper and lower instrument panel switch pods, the steering wheel switches and the automatic transmission gear selector bezel. All lamps in the non-dimming panel lamps circuits are provided a path to ground at all times through a hard-wired ground circuit. These lamps are illuminated by outputs of the BCM using internal high side drivers through the non-dimming panel lamps circuits.

  The Instrument Panel Cluster (IPC) and the radio use "electronic backlights without dimmer" bus messages from the BCM to control the illumination intensity of their own backlighting and controls.