GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Envoy - 2WD 🢒 Body Systems 🢒 Lighting 🢒 DTC B0951

Circuit 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.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B0951 Headlamps On Indicator Circuit

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC
    • The LED dimming signal circuit is open.
    • The LED dimming signal circuit is shorted to ground.
    • The LED dimming signal circuit is shorted to voltage.
    • There is a loss of the rear fuse block truck body controller (TBC) 5 battery supply voltage to the BCM for more than 1 second.

Action Taken When the DTC Sets

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

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. Tests for an open in the TBC 5 battery positive voltage supply circuit within the body wiring harness extension harness.

    2.

  2. Tests for voltage at the LED dimming signal circuit.

    3.

  3. Tests for voltage at the LED dimming signal circuit when the headlamp switch is in the OFF position.

    4.

  4. 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 Data Communication Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool to control the backlight dimming.
  4. Activate the affected control switch.

Does the control switch indicator lamp respond to the scan tool output control?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Test the truck body controller (TBC) 5 battery positive supply voltage circuit of the body wiring harness extension harness for continuity. Refer to Circuit Testing .

Is continuity present?

Go to Step 4

Go to Step 7

4

  1. Turn the headlamp switch to PARK.
  2. Adjust the instrument panel (I/P) dimmer switch to the full illumination position.
  3. Probe the LED dimming signal circuit with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 9

5

  1. Turn the headlamp switch to the OFF position.
  2. Ensure that there is sufficient light to the ambient light sensor to prevent automatic lamp control (ALC) activation.
  3. Probe the LED dimming signal circuit with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 6

Go to Step 8

6

Test the LED dimming signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 8

7

Inspect for poor connections at the body wiring harness extension harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 10

8

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 12

Go to Step 11

9

Repair the open, high resistance or short to ground in the LED dimming signal circuit. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 12

--

10

Replace the body wiring harness extension harness to the BCM. Refer to Body Control Module Body Wiring Harness Extension Harness Replacement for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 12

--

11

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 12

--

12
  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