For 1990-2009 cars

### Circuit Description

Daytime running lamps (DRL) are controlled by the body control module (BCM) based on input from the high beam headlight circuit 1200, the low beam headlight circuit 1201, the parking brake circuit 1134, and the ignition switch state.

When DRL operation is desired, the BCM switches circuit 592 to ground. This action energizes the DRL relay. When energized, the DRL relay operates the left high beam headlight and right high beam headlight as a series circuit, with one-half of battery voltage across each high beam headlight.

When DRL operation is not desired, the BCM does not provide ground for the DRL relay. When not energized, as when high beam headlights are desired, the DRL relay operates the right and left high beam headlights as a parallel circuit, with full battery voltage across each high beam headlight.

For DRL operation, the parking brake must be fully released, the ignition switch must be in the RUN position, and the headlight switch must be in the OFF position. Under normal operating conditions, the feedback voltage to the BCM measured at circuit 1200 is 6-8 volts.

### DTC Parameters

• | The ignition is in the RUN position.

• | The DRL is commanded OFF.

• | Circuit 592 is shorted-to-ground or open.

### Diagnostic Aids

• | Check for a poor connection at the BCM. Inspect the harness connectors for backed out terminals, improper terminal mating, broken connector locks, improperly formed or damaged terminals, and poor terminal-to-wire connection (terminal crimped over wire insulation and not conductors).

• | Inspect the wiring harness for damage. Check for broken or chaffed insulation.

• | If a fault is suspected to be intermittent, wiggling the harness wiring may help in locating the fault.