Headlamp: Description and Operation

HEADLAMPS
The headlamps may be turned ON 2 different ways. First, when the headlamp switch is placed in the headlamps position, for normal operation. Second, with the headlamp switch placed in the AUTO position, for automatic lamp control (ALC). During ALC, the headlamps will be in daytime running lamp (DRL) operation in daylight conditions, or headlamp operation in low light conditions.

For headlamp operation, battery positive voltage is applied at all times to the coil and switch sides of the low or high beam relay in the underhood fuse block depending on the position of the headlamp dimmer switch. Ground to the headlamp switch is from G200. When the headlamp switch is placed in the HEAD position, ground is applied to the headlamp switch headlamps ON signal circuit of the body control module (BCM). When either the headlamp switch is placed in the headlamps position or ALC is enabled, the BCM applies a ground to the headlamp low or high beam relay control circuit. This energizes the relay and applies battery positive voltage to the left and right low or high beam fuses in the underhood fuse block, then through the headlamp supply voltage circuits to the headlamps. Ground is applied at all times to the left headlamp from G101 and to the right headlamp from G100.

For high beam operation, the dimmer switch supplies a ground signal to the BCM. Ground to the headlamp dimmer switch is from G200.

For flash-to-pass (FTP) operation, when the headlamp dimmer switch is placed in the FTP position, ground is applied from G200 through the headlamp dimmer switch to the FTP switch signal circuit to the BCM. The BCM then turns the high beam headlamps ON as long as the headlamp dimmer switch is held in the FTP position.

If the headlight switch is left in the headlamps position, the inadvertent power control feature will turn OFF the headlights 10 minutes after the ignition switch is turned to the OFF position. If the driver places the headlight switch in the headlamps 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.