For 1990-2009 cars

## Headlights/Daytime Running Lights (DRL) Circuit Description Buick

The daytime running lamps (DRL) activate under the following conditions:

• | The ignition switch is in the RUN position.

• | The ambient light sensor indicates daylight.

• | The vehicle is not in the PARK position.

When the above conditions are met, the lamp control module (LCM) supplies battery positive voltage (B+) through CKT 589 (GRY) to the high beam headlamps in series. Because the high beam headlamps are in series, they split the voltage supplied by the LCM and the high beam headlamps light at a reduced intensity. The DRL are disabled if the vehicle is in PARK. When the ambient light sensor indicates darkness the low beams automatically light at regular intensity and the high beams go out.

## Headlights/Daytime Running Lights (DRL) Circuit Description Oldsmobile/Pontiac

The daytime running lamps (DRL) activate under the following conditions:

• | The ignition switch is in the RUN position.

• | The ambient light sensor indicates daylight.

• | The vehicle is not in the PARK position.

When the above conditions are met, the lamp control module (LCM) supplies battery positive voltage (B+) to the low beam headlamps through CKT 589 (GRY), the DRL resistor, and CKT 12 (TAN). The DRL resistor reduces the voltage supplied by the LCM. The low beam headlamps light at a reduced intensity. The DRL disable if the vehicle is placed in the PARK position. When the ambient light sensor indicates darkness, the low beam headlamps automatically switch from a reduced intensity to a regular intensity.