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 B2625 00: Display Dimming Pulse Width Modulation (PWM) Output Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

IS LPS Fuse B+

B1395 03

B1395 03

--

--

Headlamp and Panel Dimmer Switch Signal

B1395 03

1

1

--

I/P Lamps Dimmer Switch Signal

B2652 00

1

1

--

I/P Dimming Voltage Reference

B1395 03

1

1

--

Indicator Dimming Control

B2625 00

1

1

--

LED Backlight Dimming Control

B2610 00

1

1

--

Headlamp and Panel Dimmer Switch Ground

--

1

--

--

1. Interior Backlighting Malfunction

Circuit/System Description

The instrument panel (I/P) dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) provides a low reference signal and a B+ voltage reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the I/P lamps supply voltage circuit and the interior backlighting components dim to the requested level.

Conditions for Running the DTC

    • Battery voltage must be between 9-16 volts.
    • Park lamps ON.

Conditions for Setting the DTC

DTC B2625 00 will set when the BCM detects a short to ground in the LED indicator dimming control circuit.

Actions Taken When the DTC Sets

When DTC B2625 00 is present, the BCM will not illuminate the LEDs supplied by the LED indicator dimming control circuit.

Conditions for Clearing the DTC

    • The condition responsible for setting the DTC no longer exists.
    • A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

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 Verification

Ignition ON, headlamp switch to PARK, vary the interior lamp dimming switch from dim to full bright. The LED lamps should dim and then become full bright.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the appropriate component.
  2. Connect a test lamp between the listed LED dimming control circuit terminal and ground.
  3. • IP multifunction switch terminal 6
    • 4wd mode switch terminal 4
    • PTO switch terminal 7
  4. Command the dimming test high to low with a scan tool. The test lamp should turn from bright to dim when changing between the commanded states.
  5. If the test lamp is always OFF, test the control circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the BCM.
    If the test lamp is always bright, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
  6. If all circuits test normal, test or replace the appropriate component.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    • Refer to the appropriate replacement procedure for the component causing the condition.
    •  Control Module References for BCM replacement, setup, and programming