Daytime Running Lamp Control Unit: Description and Operation

The DRL control module is designed to automatically operate the exterior lights depending on the outside light conditions.

The DRL control module operates in the following 2 modes:
- The day mode
In the day mode, the DRL ambient light sensor senses daylight then the DRL control module activates the front turn lamps (non-flashing) under the following conditions:
- The ignition is in RUN.
- The headlamps are OFF.
- The park brake is OFF.
- The night mode
In the night mode, the DRL ambient light sensor senses darkness turning off the front turn lamps and turning on the headlamps through CKT 10.

Also in the night mode, the DRL ambient light sensor activates the following lamps through CKT 9:
- The park lamps
- The side marker lamps
- The license lamps
- The tail lamps
- Voltage is also fed back through CKT 9 to the headlamp switch assembly to control IP dimming.

If the engine should stall with the DRL control module in the night mode, the DRL control module will turn off the headlamps, leaving the side marker, park, license and tail lamps in the ON position while the engine is being cranked. The headlamp and instrument panel lamp dimmer switch operate as usual.

The DRL control module receives voltage from the DRL Fuse through CKT 1839 and the HVAC/DRL Fuse through CKT 241. The park lamps and/or the headlamps may be operated manually at any time by using the headlamp and the Instrument Panel (IP) lamp dimmer switch. The DRL module will not operate if the system voltage is less than 9 volts or greater than 18 volts.