With Daytime Running Lights (DRL)
WITHOUT FOG LIGHTSWith the Ignition Switch in "RUN," the Light Switch not in "HEAD" and the Park Brake released, the Daytime Running Lights (DRL) Module grounds the coil of the DRL Relay. The relay is energized, and battery voltage is applied to the ground side of the LH HI Beam Headlight, allowing voltage to also be applied to the RH HI Beam Headlight. This series circuit arrangement causes the voltage across each HI Beam Headlight to be exactly half the battery voltage, reducing Headlight brilliance for the DRL mode operation.
When the Light Switch is in "HEAD" and the Headlight Dimmer Switch is in "LO," battery voltage is applied to the Light Switch Input of the DRL Module via CKT 10. The module de-energizes the DRL Relay, applying ground to the LH HI Beam Headlight. Battery voltage is applied to the LO Beam Headlight filaments via CKT 12.
When the Light Switch is in "HEAD" and the Headlight Dimmer Switch is in "HI," battery voltage is applied to the HI Beam Input of the DRL Module via CKT 11. The Module de-energizes the DRL Relay, removing voltage from CKT 593 and disengaging DRL mode operation. With the relay de-energized, the ground path through the DRL Relay to the LH HI Beam Headlight is restored. Battery voltage is applied to the HI Beam Headlights via CKT 11.
The Daytime Running Lights (DRL) Module has an input from the BRAKE Indicator control circuit. When the Park Brake is set, ground is applied to the DRL Module Park Brake Applied Input. The DRL Module then removes ground from the DRL Relay, and the relay is de-energized, removing battery voltage from the HI Beam Headlights. Because the Park Brake Switch shares CKT 33 with the Electronic Brake Control Module (EBCM) and the Brake Fluid Level Switch, any condition that causes the BRAKE Indicator to come on will also inhibit the HI Beam Headlights from operating in Daytime Running Lights mode.
WITH FOG LIGHTS
With the Ignition Switch in "RUN," the Light Switch not in "HEAD" and the Park Brake released, the Daytime Running Lights (DRL) Module grounds the coil of the DRL Relay. The relay is energized, and battery voltage is applied to the Fog Lights through the contacts of the DRL Relay. The Fog Lights operate at full brilliance for the DRL mode operation.
When the Light Switch is in "HEAD" and the Headlight Dimmer Switch is in "LO," battery voltage is applied to the Light Switch Input of the DRL Module via CKT 10. The Module de-energizes the DRL Relay, turning off the Fog Lights. Battery voltage is applied to the LO Beam Headlights via CKT 12
When the Light Switch is in "HEAD" and the Headlight Dimmer Switch is in "HI," battery voltage is applied to the HI Beam Input of the DRL Module via CKT 11. The Module de-energizes the DRL Relay, turning off the Fog Lights. The Module also supplies voltage to the HI Beam Indicator via CKT 629. Battery voltage is applied to the HI Beam Headlights via CKT it.
With the Light Switch in "PARK" or "HEAD," battery voltage is applied to the Fog Light Switch. With the LO Beam Headlights on and the Fog Light Switch "ON," battery voltage is applied to the coil of the Fog Light Relay. The Fog Light Relay coil receives its ground signal through the DRL Module. The relay is energized, and voltage from the FOG Fuse is applied to the Fog Lights through the Fog Light Relay contacts. If the HI Beam Headlights are turned on, battery voltage is applied to the HI Beam Input of the DRL Module. The DRL Module removes ground from the Fog Light Relay, and the relay is de-energized, removing battery voltage from the Fog Lights.