When the ignition switch is in the RUN position, the ambient light sensor indicates daylight, and the gear selector is not in the PARK position, the daytime running lights (DRL) are activated. When these conditions are met, the lamp control module (LCM) supplies battery positive voltage (B+) through CKT 593 (DK BLU) to the high beam headlamps in series. Because the high beam headlamps are in series, they split the voltage supplied by the LCM. The high beam headlamps light at a reduced intensity. The DRL are disabled if the gear selector is placed in the PARK position. When the ambient light sensor indicates darkness, the low beams automatically turn on at regular intensity and the high beams go out.

When the ignition switch is in the RUN position, the ambient light sensor indicates daylight, and the gear selector is not in the PARK position, the daytime running lights (DRL) are activated. When these conditions are met, the lamp control module (LCM) supplies battery positive voltage (B+) through the DRL resistor to the low beam headlamps. The voltage drop across the DRL resistor causes the low beam headlamps to light at a reduced intensity. The DRL are disabled if the high beam headlamps are on or if the gear selector is placed in the PARK position. When the ambient light sensor indicates darkness, the low beams automatically switch to regular intensity.