The daytime running lamps (DRL) operate automatically, provided that the following conditions exist:

When the DRL is operating, the low beam headlamps are on. The low beam headlamps shine slightly dimmer in the DRL mode than they would if the headlamps were operating form the headlamp switch.

The system is comprised of the following components:

The DRL control module senses normal headlamp operation by receiving a voltage input through terminal D in the module, when the headlamp switch is in the HEAD position. The signal disables the DRL mode when normal headlamp operation is desired. A ground input at terminal A in the module will also disable the DRL mode. The ground is provided through the ignition switch when starting the engine or through various configurations of park brake circuits when the park brake engages.

When the system operates normally, the DRL module receives a voltage input through terminal C when the following conditions exist:

The absence of inputs at terminals A (headlamp switch) or D (park brake) will cause the DRL Module to provide a system ground through terminal G. The daytime running light relay and the (green) DRL indicator lamp also receives a voltage input when the ignition switch is in the RUN position. The ground at terminal G will cause the daytime running light relay to energize, and the DRL indicator lamp to light. When the daytime running light relay energizes, the relay contacts the switch, and the low beam headlamps then receive their power from the headlamp switch, through the daytime running light diode module. The daytime running light diode module acts as a series voltage dropping device, which reduces supplied voltage to the headlamps. This causes the low beam headlamps to shine slightly dimmer in the DRL mode.