GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B0951 00: Headlamps On Indicator Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

LED Dimming Control

B0591, B2625

B0591

--

--

Headlamp On Indicator Control

--

1

1

--

1. Headlamp on indicator inoperative

Circuit/System Description

The body control module (BCM) controls the illumination dimming of all of the control switch indicators. The BCM will set the control switch indicator illumination level according to the instrument panel (I/P) dimmer switch signal received when the component is activated and the indicator is ON.

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The LED dimming control circuit is open or shorted to ground.

Action Taken When the DTC Sets

The control switch indicators will not operate or will not dim.

Conditions for Clearing the DTC

    • This DTC will clear on current status after the condition for setting the fault is corrected.
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.

Reference Information

Schematic Reference

Interior Lights Dimming Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Interior Lighting Systems Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

  1. Ignition OFF, disconnect the headlamp switch connector X1.
  2. Connect a test lamp between the LED dimming control circuit terminal K and ground.
  3. Park lamps ON, operate the IP dimmer switch between bright and dim. The test lamp should illuminate bright to dim.
  4. If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If all circuits test normal, replace the BCM.
    If the test lamp remains illuminated bright, test the control circuit for a short to voltage. If all circuits test normal, replace the BCM.
  5. If all circuits test normal, replace the headlamp switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, programming, and setup