Headlamps

The headlamps may be turned on in two different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for Automatic Lamp Control (ALC). During ALC control the headlamps will be in Day Time Running Lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions.

The automatic lamp control (ALC) system and the DRL feature can be temporarily disabled by performing the following procedure:

NOTE: The ALC and DRL cannot be turned off on the Canadian vehicles.

1. Turn the ignition to RUN.
2. Press the DOME OVERRIDE button four times within six seconds.

A chime will sound informing you that the system is off. The system will remain disabled until the ignition is cycled off and then on or by pressing the DOME OVERRIDE button four more times within six seconds. The chime will sound again signaling that the system has been reactivated.

The engine wiring harness junction block supplies battery positive voltage to the normally open headlamp relay switch circuit. The TBC 10 A fuse in the engine wiring harness junction block supplies battery positive voltage to the headlight and dimmer switch assembly. The Body Control Module (BCM) also supplies battery positive voltage to the headlamp relay coil circuit for automatic headlight control. The coil circuit of the headlamp relay is then grounded at G102 When the driver places the headlamp switch in the HEADLAMP position, the headlamp relay is energized. Depending on the position of the dimmer switch, the current flow is to both the left and right headlamp fuse, and to either the low or high beam headlamps. From the dimmer switch, the current flow is to ground at G203. The TCB 10 A fuse in the engine wiring harness unction block supplies battery positive voltage to the headlight and dimmer switch assembly flash to pass switch. When the headlamp dimmer switch handle is pulled toward the driver, both flash-to-pass switches close, one grounding the high beam circuit at G203. A second flash to pass switch also closes providing battery positive voltage to the BCM flash-to-pass input. With the headlights in the low beam position, the high beams may be momentarily turned on or flashed with the dimmer switch handle.

If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights approximately 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the ON position after the ignition switch has been turned OFF, or if the ignition switch is in the ACCY position, the headlights will remain on until turned off or the battery runs dead.

The high beam indicator is illuminated when the instrument cluster receives a class 2 serial data message from the BCM that the high beams are illuminated.