Automatic Lamp Control/Twilight Sentinel

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

To turn on or off the automatic lamp control/twilight sentinel feature:

Turn the ignition switch to the ON position.
Press the OPTIONS button located on the DIC, until the twilight option appears.
Press the RESET button to the desired mode.

Place the headlamp switch in the OFF position, for automatic lamp control (ALC). During ALC control the headlamps will be OFF during daylight conditions but will turn ON when the ambient light sensor detects low light level. The ambient light sensor is a light sensitive transistor that varies its voltage signal to the body control module (BCM) in response to changes to the outside (ambient) light level. The BCM will apply a ground to the coil side of the ALC HDLP relay 44. This energizes the relay, closing the switch and applies battery positive voltage to the headlamp switch and to the headlamp opening door actuator control module. With the headlamp switch in the OFF position battery positive voltage is then applied from the headlamp switch to the HDLOBML fuse and HDLOBMR fuse in the underhood fuse block. Battery positive voltage is then applied from the fuse to the individual headlamps. The ground circuit for the left headlamps is provided from G101 and the ground circuit for the right side is provided by G102 for low beam operation in low light conditions.

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 until the battery runs dead.