Circuit Operation - Exterior Lights

DAYTIME RUNNING LAMPS
The Daytime Running Lamps (DRL) control module is designed to automatically operate the exterior lights depending on outside light conditions. The DRL control module operates in two modes. In the day mode, the two front turn signal lamps are on (non flashing). In the night mode, the low beam headlamps are on and the front marker, park and tail lamps are on.

When the DRL ambient light sensor senses darkness, the DRL control module operates in the night mode. The night mode contacts close, applying voltage to the headlamps and other exterior lights through the same circuit path as when the headlamp switch is in the HEAD position.

If the engine should stall with the DRL control module in the night mode, the DRL control module will turn off the headlamps and leave the marker, park and tail lamps on while the engine is being cranked. The headlamp switch operates as usual.

DAYTIME RUNNING LAMPS (DRL) AMBIENT LIGHT SENSOR INPUT
The DRL ambient light sensor is a light sensitive variable resistor. Its resistance decreases as outside light intensity increases. The DRL control module measures the voltage drop across the DRL ambient light sensor and determines whether it should operate in the day mode or night mode.

PARK BRAKE INPUT
If the park brake is applied before the ignition switch is turned to the RUN position the DRL control module will not operate any headlamps or exterior lamps. This allows the operator to start the vehicle and keep the headlamps off, as long as the park brake is applied. When the park brake is released with the ignition switch in the RUN position, the DRL control module will activate the headlamps.

This feature will only function when the park brake is applied before the ignition switch is turned to the RUN position. If the park brake is applied after the ignition switch is turned to the RUN position, the headlamps will not turn off.

FRONT PARK AND FRONT SIDE MARKER
Voltage is applied from the FRT PARK LPS Fuse when ever the park lamps are on, through circuit 9 to the Underhood Electrical (UH) center then to both front side marker lamps' and front park lamps.

REAR PARK, REAR SIDE MARKER, TAIL AND LICENSE PLATE LAMPS
Voltage is applied at all times from the LP PARK Fuse to the Headlamp Switch and DRL control module through circuit 1340. With the headlamp switch in the PARK or HEAD position, voltage is applied to circuit 74. Current flows through circuit 74 to the TAIL LAMP Fuse through circuit 301, to all rear park, rear side marker, tail and license plate lamps turning them on.

TURN SIGNAL LAMPS
With the ignition switch in the RUN, BULB TEST or START position, voltage is applied from the TURN SIGNAL Fuse to the normally closed pole of the hazard switch in the turn signal switch through circuit 539, which feeds the hazard lamp/turn signal lamp flasher through circuit 1508. With the turn signal switch in the turn left position, voltage is applied through two circuits from the turn signal switch circuit 1414 at terminal A13 of connector C201 and circuit l8at terminal E10 of C201. For circuit 1414 voltage flows through circuit 1414 to the instrument cluster for the left turn telltale and to the daytime running lamps control module then through circuit 14 to the Underhood (UH) electrical center to the LH front turn signal lamp. For circuit 18, voltage flows through circuit 18 to the LH rear turn signal lamp. Current flow heats the timing element in the hazard lamp/turn signal lamp flasher, and it continuously opens and closes the circuit for RH turn signal lamps, circuit 1415 terminal A12 of C201 and circuit 19 terminal E11 of C201.

HAZARD LAMPS
Voltage is applied at all times from HAZARD Fuse to the normally open poles of the hazard switch in the turn signal switch through circuit 1840. With the hazard switch in the HAZARD position, voltage is applied to hazard lamp/turn signal lamp flasher through circuit 1508, current flow heats the timing element in the hazard lamp/turn signal lamp flasher, and it continuously opens and closes circuit 16 to the turn signal switch and then to all the turn signal lamps and both turn telltale lamps. All of the turn signal lamps and both turn telltale lamps flash on and off.

STOP LAMPS
Voltage is applied at all times from the STOP LAMPS Fuse to the stop lamp switch through circuit 140. When the brake pedal is depressed, voltage is applied from the stop lamp switch to the turn signal switch through circuit 17 turning on the LH and RH tail/stop/turn signal lamps and to the Center High-Mounted Stop Lamp (CHMSL), turning on the center high mounted stop lamp.