Envoy 4WD L6-4.2L VIN S (2003)
Daytime Running Lamp: Description and Operation
DAYTIME RUNNING LAMPS (DRL)
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. When the BCM receives this signal it will either turn on the daytime running lamps (DRL) through the HDM using the
reduced output or the headlamps at full intensity for auto headlamp operation. Any function or condition that turns on the headlights will cancel the
daytime running lamps operation. The daytime running lamps (DRL) are the low beam headlights at a reduced intensity. With the headlight switch in the
OFF position, the headlights will either be turned ON or OFF, after an approximate 8 second delay depending on whether daylight or low light
conditions are sensed. When the BCM signals the HDM for DRL operation in daylight conditions, the HDM illuminates the low beam headlights at a
reduced intensity. The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in the PARK position and the parking
brake is released. When these conditions have been met and the ambient light sensor indicates daytime conditions, the DRL will illuminate.
On vehicles equipped with the 4-position headlamp switch, the DRL feature can be temporarily disabled by momentarily placing the headlamp switch in
the DRL defeat position. This will signal the BCM to disable the DRL function until the headlamp switch is momentarily placed in the DRL defeat
position again or until the next ignition key cycle.
DRL operation in Manual Transmission equipped vehicles will occur when the ignition switch is in the RUN position, and the parking brake is released.
