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

DIM Fuse B+

2

2

--

--

I/P Dimmer Voltage Reference

B1395 03 and B3600 03

B1395 03, B2652 00, and B3600 03

B1395 07

--

IS LPS Fuse B+

2

2

--

--

I/P DImmer Switch Signal

B1395 03

2

2

--

Stop Lamp Switch Signal

B1395 03 and B3600 03

3

3

--

I/P Dimming Control

B2625 00 and B2652 00

2

2

--

LED DImming Supply

B2610 00 and, B2625 00

B2610 00

B2610 00

--

Park Lamp Control

2

2

2

--

Indicator Dimming Low Reference

2

2

2

--

I/P Dimmer Switch Low Reference

--

1

--

--

I/P Dimmer Switch Ground

--

2

--

--

1. Dimmer Switch Malfunction

2. Interior Backlighting Malfunction

3. Stop Lamp Switch 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 are 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.

Action 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 conditions for setting the DTC are no longer present.
    • A history DTC clears after 100 malfunction-free ignition cycles.
    • The BCM receives the clear code command from the scan tool.

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 harness connector at the inoperative component.
  2. Connect a test lamp between the listed indicator dimming control circuit terminal and ground.
  3. • I/P Multifunction Switch terminal 1 X1
    • Transfer Case Shift Control Switch terminal 4
    • Headlamp and Panel Dimmer Switch terminal 11
  4. Command the LED 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 inoperative 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
    •  Transfer Case Shift Control Switch Replacement
    •  Headlamp Switch Replacement