GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) flashes the headlamps and pulses the horns when a theft attempt is detected. The BCM grounds the headlamp and parklamp control circuits via a descrete input of the daytime running lamps (DRL) control module. The DRL control module actuates the headlamp and parklamp relays internal to the DRL control module.

Conditions for Setting the DTC

The BCM detects a short to battery or short to ground in the exterior lamps output circuit.

Action Taken When the DTC Sets

    • The BCM sets the diagnostic trouble code (DTC) 6.
    • The BCM does not turn on the headlamps during the armed, warning, or alarm modes.

Conditions for Clearing the DTC

A short to battery or short to ground in the exterior lamps output circuit is no longer present between the BCM and the DRL control module.

Diagnostic Aids

    • If the exterior lamps output circuit is shorted to ground, the headlamps will stay ON at all times.
    • Move the wiring and the connectors while you complete the following tests. This may cause the malfunction to appear.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step checks the integrity of the exterior lamps output circuit.

Step

Action

Yes

No

Schematic Reference: Theft Deterrent System Schematics

1

Did you perform A Diagnostic System Check-Theft Deterrent?

Go to Step 2

Go to Diagnostic System Check - Theft Deterrent

2

Perform the body control module (BCM) output test. Refer to On-Board Diagnostic Features in Body Control System.

Do the headlamps turn on for one second when the BCM performs test 4?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Disconnect the daytime running lamps (DRL) control module.
  2. Probe the exterior lamps output circuit with a test lamp connected to battery positive voltage.
  3. Activate the alarm mode using the keyless entry transmitter.

Does the test lamp flash?

Go to Step 5

Go to Step 4

4

Test for an open or short in the exterior lamps output circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 6

5

Inspect for poor connections at the harness connector of the DRL control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct a condition?

Go to Step 9

Go to Step 7

6

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

Did you find and correct a condition?

Go to Step 9

Go to Step 8

7

Replace the DRL control module. Refer to Daytime Running Lights (DRL) Control Module Replacement in Lighting Systems.

Did you complete the repair?

Go to Step 9

--

8

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

Did you complete the replacement?

Go to Step 9

--

9

  1. Clear the DTCs.
  2. Activate the alarm mode using the keyless entry transmitter.

Does the DTC reset?

Go to Step 2

System OK