Exterior Lighting Control

The BCM controls exterior lighting Systems which includes the following:
^ ALC headlamps and parklamps
^ Daytime Running Lights (DRL)
^ Front foglamps

Daytime Running Lights (DRL) operate the headlamps (Pontiac) or high beams only (Oldsmobile) at a reduced intensity under the following conditions:
^ When the vehicle is not in park
^ When the park brake is not set
^ When the normal headlamps are not on

The DRL activates if the transmission is not in PARK and the park brake is off. The DRLs remain on and latch on if the park brake is on and the vehicle speed is above the threshold. The vehicle is defined to be in motion if the transmission is not in PARK and the park brake is not set.

Automatic lighting control turns on the parklamps and the headlamps when the ambient light sensor detects a low ambient light level. The system assures that the headlamps/parklamps are on if the driver is operating the vehicle after dark.

If the ignition switch is turned to the ON position in a low ambient light level area, the automatic lighting control becomes active immediately, otherwise 8 seconds must elapse before the automatic lighting control is activated. If the park brake is set when the ignition switch is turned to the ON position, the automatic lighting control is disabled until the park brake is released. If the automatic lighting control is active and a high ambient light level is detected, 20 seconds must elapse before the automatic lighting control is turned off. The headlamps are disabled during engine crank.

The front foglamp relay activates when all of the following conditions occur:
^ The ignition switch is on.
^ The parklamps are on.
^ The highbeam headlamps are off.
^ The foglamp switch is pressed.

Foglamp relays are always off whenever a short to battery fault is detected on the foglamp relay output driver.

The backup lamps are the only exterior lamps that are not controlled by the BCM.