Daytime Running Lamp: Description and Operation

DAYTIME RUNNING LAMPS (DRL)

The daytime running lamps (DRL) are the front turn signals. The front turn signals are designed to automatically illuminate in daytime light conditions.

The ambient light sensor is a light sensitive transistor that varies its voltage signal to the daytime running lamps (DRL) control module in response to changes to the outside (ambient) light level. When the DRL module receives this signal it will either turn on the daytime running lamps (DRL) or the automatic headlamps depending on the ambient light level. When the daytime running lamps (DRL) control module detects daylight conditions, it will turn on the front turn signals.

In the daylight conditions, the ambient light sensor detects daylight and the DRL control module applies voltage to the LH and RH front turn signal lamps illuminating the lamps under the following conditions:
- The ignition switch is in the RUN position.
- The headlamps are OFF.
- The park brake is OFF (released).
- The RH or LH turn signal is OFF.

The DRL control module will not operate the daytime running lamps, if the park brake is applied before the ignition switch is turned to the RUN position. This allows the driver to start the vehicle and keep the daytime running lamps OFF, as long as the park brake is applied. The DRL control module will activate the daytime running lamps when the park brake is released with the ignition switch in the RUN position. This feature functions only when the park brake is applied before the ignition switch is turned to the RUN position.

When the turn signal switch place in either the LH or RH position, pulsating voltage is supplied to the DRL control module. The DRL control module senses the voltage and disengages the DRL function of the appropriate front turn signal. The DRL control module then relays the turn signal voltage to the front turn signal and the front turn signal will flash.