Headlamp: Description and Operation

The Daytime Running Lamp (DRL) system includes the DRL relay, the hi beam headlamps and the DRL logic which is located within the instrument panel cluster on the speedometer Printed Circuit Board (PCB). The system uses the Ignition 1, Park Brake, High Beams, and Headlamps On inputs to determine whether to turn DRL on or off.

The DRL system illuminates the high beam headlamps at half intensity to increase vehicle visibility during the daylight hours. The half intensity is achieved by using the DRL relay to connect the two high beam headlamps in a series circuit, instead of the parallel circuit during regular high beam operation.

Under any of the following conditions DRL will be turned off:
^ Parking Brake is applied.
^ Ignition is not in the RUN position.
^ Headlamp input is grounded (when low or high beam headlamps are on).
^ High Beam input is grounded (when in flash-to-pass or high beam headlamps on mode).
^ If the left high beam is open. (This is detected at the high Beam input (pin N). When DRL is active this input should be at half battery voltage. If the left high beam is open then the input will be pulled to ground when the DRL relay is energized. The DRL logic will cycle the relay several times to verify the condition and then disable DRL operation.)
^ If the right high beam is open DRL will be off.

However, if both high beam headlamps are open the DRL telltale will be illuminated because the logic cannot detect this condition.

BLACK CONNECTOR
Pin L Battery voltage (Run position only)
Pin M Battery voltage (at all times)
Pin K Continuity to ground
Pin N Zero volts (headlamps On and headlamp switch in high beam position or flash-to-pass)
Battery voltage (any other time)
Pin O Zero volts (headlamps On and headlamp switch in low beam position)
Battery voltage (any other time)
Pin H Battery voltage (Run and Crank positions only)
Pin Q Continuity to ground (with park brake On)
Open (with park brake Off)

If any of the above checks fail, repair an open/short in the malfunctioning circuit.

If all the above checks are correct, rule out all other possible causes in the cause/complaint table. If all others are ruled out, the problem is most likely the cluster (connections, flex circuits, etc.) or the DRL Logic (which is located on the speedometer gage printed circuit board). Refer to Internal Resistance Checks for Speedometer in the Radio, Stereo, and Compact Disc. Verify that the complaint has been fixed. Radio, Stereo, and Compact Disc

Repair/replace as needed.