Interior Lighting - Operation

OPERATION

The 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 non-dimming panel lamps circuit. Following are paragraphs that briefly describe the operation of each of these interior lighting circuits.

The lamps and the hard wired circuits between components related to the interior lighting system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the interior lighting system or the electronic controls or communication between modules and other devices that provide some features of the interior lighting system. The most reliable, efficient, and accurate means to diagnose the interior lighting system or the electronic controls and communication related to interior lighting system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

COURTESY LAMP CIRCUIT

The courtesy lamp circuit includes the dome/reading lamps located on the headliner near the center of the windshield opening upper header and the cargo (or trunk) lamp located on the rear edge of the left quarter inner trim near the left trunk trim panel at the rear of the vehicle. 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, the door ajar switches and the liftgate ajar switch. 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 or liftgate 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 to the BCM 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.

NON-DIMMING PANEL LAMPS CIRCUIT

The non-dimming panel lamps circuit actually includes several circuits. These circuits control the backlighting of the heater-air conditioner 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 messages from the BCM to control the illumination intensity of their own back lighting and controls.