GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 GMC Sierra Denali 🢒 DTC 🢒 DTC B0951

Circuit Description

The body control module (BCM) controls the illumination dimming of all of the control switch indicators. The BCM sets 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. The BCM also activates the headlamp on indicator.

Voltage for the LED dimming signal, instrument panel lamps dimming control, as well as the instrument panel lamps dimming supply voltage circuits is from the TBC 2 A fuse in the instrument panel fuse block directly through the BCM to these circuits.

Conditions for Running the DTC

The battery voltage must be between 9.0-16.0 volts.

Conditions for Setting the DTC
    • The headlamp on indicator control circuit is open, shorted to ground, or shorted to voltage.
    • The LED dimming signal circuit is open, shorted to ground, or shorted to voltage.
    • The instrument panel lamps dimming control circuit is shorted to ground.
    • There is a loss of the instrument panel fuse block TBC 2 A battery supply voltage to the BCM for 1 second.

Diagnostic Aids
    • Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • A short to ground in the following circuits will cause the TBC 2 A fuse to open.
       - The instrument panel lamps dimming control.
       - Battery positive voltage from the instrument panel fuse block TBC 2 A fuse.
    • An open in the TBC 2 A fuse will cause the BCM to set the following DTC:
       - B0951
       - B2610
       - B2625

Action Taken When the DTC Sets

The headlamps on indicator will remain on with the headlamps off.

The headlamps on indicator will remain off with the headlamps on.

Conditions for Clearing the MIL/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.
    • History and current DTCs can be cleared using a scan tool.

Test Description

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

  1. Determines if it is the headlamp on indicator circuit or the BCM.

    2.

  2. Determines if it is the headlamp on indicator circuit or the BCM.

    3.

  3. After replacement of the BCM you must calibrate the new module for proper operation.

Step

Action

Yes

No

Schematic Reference: Interior Lights Dimming Schematics

Connector End View Reference: Lighting Systems Connector End Views or Body Control System Connector End Views in Body Control System

1

Did you perform the Lighting Systems Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2
  1. Turn ON the ignition with the engine OFF
  2. Observe the headlamp on indicator.
  3. Place the headlamps in the ON position.
  4. Rotate the headlamp and panel dimmer switch to the dim position and then to the full bright position.

Does the headlamp on indicator respond as expected?

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

Go to Step 3

3

Is the TBC 2 A fuse in the instrument panel fuse block open?

Go to Step 4

Go to Step 5

4

Test the following circuits for a short to ground:

    • LED dimming signal
    • Instrument panel lamps dimming control

Did you find and correct the condition?

Go to Step 16

Go to Step 13

5

Connect a test lamp between the LED dimming signal circuit of the headlamp switch and a good ground.

Does the test lamp illuminate?

Go to Step 6

Go to Step 7

6

Test the LED dimming signal circuit of the headlamp switch for a short to voltage.

Did you find and correct the condition?

Go to Step 16

Go to Step 8

7

Test the LED dimming signal circuit of the headlamp switch for a high resistance or an open.

Did you find and correct the condition?

Go to Step 16

Go to Step 12

8

Test for a ground signal on the headlamp on indicator control circuit at the headlamp switch.

Is a signal present?

Go to Step 9

Go to Step 10

9

Test the headlamp indicator control circuit of the headlamp switch for a short to ground.

Did you find and correct the condition?

Go to Step 16

Go to Step 11

10

Test the headlamp on indicator control circuit for a high resistance, an open, or a short to voltage.

Did you find and correct the condition?

Go to Step 16

Go to Step 12

11

Inspect for poor connections at the harness connector of the headlamp switch. 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 16

Go to Step 14

12

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 the condition?

Go to Step 16

Go to Step 15

13

Repair the battery positive voltage circuit of BCM from the TBC 2 A fuse from the instrument panel fuse block.

Did you complete the repair?

Go to Step 16

--

14

Replace the headlamp and panel dimmer switch. Refer to Headlamp Switch Replacement .

Did you complete the replacement?

Go to Step 16

--

15

Important: Perform the setup procedure for the BCM.

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

Did you complete the replacement?

Go to Step 16

--

16
  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