GM Service Manual Online
For 1990-2009 cars only

Circuit Description

With the ignition switch in the ON position, the Body Control Module (BCM) supplies battery positive voltage to the HEADLAMPS relay coil, and the PARK LAMPS relay coil. The BCM monitors the voltage on the headlamp relay coil supply voltage circuit every 300 ms.

Conditions for Running the DTC

    • The Ignition switch is in the ON position.
    • The exterior lamps are commanded on for at least 300 ms.

Conditions for Setting the DTC

The headlamp relay coil supply voltage circuit is low for at least 600 ms.

Action Taken When the DTC Sets

The BCM turns OFF the exterior lamps output, until the condition for setting the DTC is no longer present.

Conditions for Clearing the DTC

The DTC will clear when the voltage on the headlamp relay coil supply voltage circuit is no longer low for at least 600 ms.

Step

Action

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Test for a short to ground in the supply voltage circuit of the HEADLAMP relay coil. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 5

Go to Step 3

3

Inspect for poor connections at the harness connector of the Body Control Module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 5

Go to Step 4

4

Replace the Body Control Module (BCM). Refer to Body Control Module Replacement in Body Control System.

Is the repair complete?

Go to Step 5

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5

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK