Monte Carlo V6-3.8L SC VIN 1 (2004)
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 in the
outside (ambient) light level. When the BCM receives this signal, the BCM turns ON either the DRL lamps or the headlamp relay for auto headlamp
operation. Any function or condition that turns ON the headlamps will cancel the DRL operation.
Thirty seconds after you start the ignition with the headlamp switch set in the OFF position, the DRL will perform one of two actions:
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Illuminate the high beam headlamps at a reduced intensity in daylight conditions
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Illuminate the low beam headlamps in low light conditions
Battery positive voltage is applied at all times from the DRL/EXT LTS fuse in the underhood junction block to the coil side of the DRL relay. When
the ambient light sensor indicates a day light condition, the BCM applies a ground to the DRL relay control circuit. This energizes the DRL relay
allowing a ground to be applied from G101 through the DRL relay switch side to the left high beam headlamp.
When the DRL relay is energized, battery positive voltage is applied from the EXT LTS fuse through the right high beam headlamp, to the left high
beam headlamp. The high beam headlamps are now in series, and split the voltage so that the headlamps illuminate a half intensity. The DRL operates
when the ignition switch is in the RUN position, and the parking brake is not set or the transmission is not in park. When these conditions have been
met and the ambient light sensor indicates daytime conditions, the DRL will illuminate.
