Express 1500 RWD V8-5.3L VIN T (2004)
Daytime Running Lamp: Description and Operation
DAYTIME RUNNING LAMPS (DRL)
The DRL are a function of the front turn signal lamps. The DRL will operate when the ignition switch is in the RUN position, the gear selector is not in
the PARK position, and the headlamp switch is in the OFF position. When the BCM receives these signals it will signal the turn/hazard flasher module to
turn on the DRL by grounding the DRL low control signal. The turn/hazard flasher module supplies voltage to the DRL on the right and left DRL/turn
supply voltage circuits. If a front turn signal lamp is inoperative the DRL will not operate.
The DRL can be deactivated by turning the headlamp switch to the DRL OFF position while the DRL are operating. The DRL defeat position of the
headlamp switch is a momentary ground signal to the BCM to command the DRL function ON or OFF. After each key cycle the BCM will default to the
DRL ON function.
