GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The body control module (BCM) receives a variable voltage signal from the instrument panel (I/P) dimmer switch requesting to illuminate the instrument panel controls illumination lamps to a desired intensity. When this occurs, the BCM directly sends a variable voltage based on the I/P dimmer switch position on the backlight lamps control circuit, instrument panel lamps dimming control circuit, and the LED dimming signal circuit.

Voltage for the backlight lamps control circuit, instrument panel lamps dimming control circuit, and the LED dimming signal circuits is from the TBC 3 fuse 16 in the underhood fuse block directly through the BCM to these circuits.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2610 Passenger Compartment Dimming 1 Circuit

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

    • The backlight lamps control circuit is open, shorted to ground, or shorted to battery positive voltage.
    • The I/P lamps dimming control circuit is open, shorted to ground, or shorted to battery positive voltage.
    • The LED dimming signal circuit is shorted to ground.
    • There is a loss of the underhood fuse block TBC 3 battery supply voltage to the BCM for 1 second.

Action Taken When the DTC Sets

The I/P illumination lamps and the controls illumination lamps will not operate or are always 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.

Diagnostic Aids

    • Perform a visual inspection for loose or poor connections at all related components. Refer to Testing for Intermittent Conditions and Poor Connections.
    • A short to ground in the following circuits will cause the TBC 3 fuse to open:
       - The backlight lamps control
       - The instrument panel lamps dimming control
       - The LED dimming signal
       - Battery positive voltage from the underhood fuse block TBC 3 fuse
    • An open in the TBC 3 fuse will cause the BCM to set the following DTC:
       - B0951
       - B2610
       - B2625

Test Description

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

  1. This step test determines if the problem exists in the headlamp switch or the BCM.

  2. 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

Is the TBC 3 fuse in the underhood fuse block open?

Go to Step 3

Go to Step 4

3

Test the following circuits for a short to ground:

    • Backlight lamps control
    • Instrument panel (I/P) lamps dimming control
    • LED dimming signal

Did you find and correct the condition?

Go to Step 11

Go to Step 8

4

Test the backlight lamps control circuit and the I/P lamps dimming control circuit for the following:

    • An open
    • A high resistance
    • A short to battery positive voltage
    • A short to ground

Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

Go to Step 11

Go to Step 5

5

  1. Ensure that the headlamp switch is in the ON position.
  2. Ensure that the I/P dimmer switch is the full bright position.
  3. With the headlamp switch still connected, connect a test lamp between the backlight lamps control circuit and the I/P lamps dimming control circuit of the headlamp switch connector.

Does the test lamp illuminate?

Go to Step 6

Go to Step 7

6

Inspect for poor connections at the harness connector of the headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

7

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.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Repair the battery positive voltage circuit of BCM from the TBC 3 fuse in the underhood fuse block.

Did you complete the repair?

Go to Step 11

--

9

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

Did you complete the replacement?

Go to Step 11

--

10

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

Did you complete the replacement?

Go to Step 4

--

11

  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