Daytime Running Lamp Control Unit: Description and Operation

The DRL Module has voltage applied at all times through CKT 240, voltage applied in "RUN," "BULB TEST" or "START" through CKT 39, and voltage applied in "RUN" through CKT 350. The DRL Module uses inputs from the DRL Sensor, through CKTs 1137 and 1138, and the Park Brake Switch through CKT 1134 to control the Park Lamp Relay. With a low light condition, ignition Switch in "RUN" and Park Brake released, the DRL Module energizes the Park Relay turning "ON" the Park Lamps (as described in Park, Marker, Tail and License Lamps).

If the Ignition Switch is turned to "RUN" after the Park Brake is set, the DRL Module will not turn on the Park Lamps until the Park Brake is released. The DRL Module will turn off the Park Lamps whenever the DRL Sensor detects a daylight condition.