Headlamp: Description and Operation

HEADLAMPS
The headlamps may be turned on two different ways. First, when the driver places the headlamp switch is placed in the ON position, for normal operation. Second, with the headlamp switch placed in the OFF 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.

Voltage is applied at all times to the coil side and the switched side of both the HDLP Low Beam relay and the HDLP High Beam relay. When the headlamp switch is in the HEAD position, a ground signal is applied from G201 to the headlamp switch. The headlamp switch supplies the ground circuit to the BCM.

The BCM then applies a ground through the headlamp relay control circuit to the headlamp dimmer switch. Depending on the switch position, the ground circuit is applied to the coil side of either the HDLP Low beam relay or the HDLP High beam relay. This energizes the coil and closes the switch. Depending on the headlamp switch position, voltage is then applied through the relay to the Low Beam LT and Low Beam RT Fuse or to the High Beam LT and High Beam RT fuse. Voltage is then supplied to the respected headlamps. The left headlamp receives it ground circuit from G101 and the right headlamp high beam receives it ground circuit from G100.

If the headlight switch is left in the ON position, the inadvertent power control feature will turn off the headlights approximately 30 seconds 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.