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 : Passenger Compartment Dimming Request Signal Circuit Voltage Below Threshold

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Body Control Module (BCM) 1 Fuse B+

B1395 03

B1395 03

--

--

Body Control Module (BCM) 7 Fuse B+

B2652 00

B2652 00

--

--

I/P Dimming Voltage Reference

B1395 03

1

1

--

I/P Dimmer Switch Signal

B1395 03

1

1

--

I/P Lamps Dimmer Switch Signal

B2652 00

1

1

--

Indicator Dimming Control

B2625 00

1

1

--

LED Backlight Dimming Control

B2610 00

1

1

--

I/P 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 Testing

  1. Ignition OFF, disconnect the harness connectors at the following components:
  2. • LH hush LED
    • LH light pipe LED
    • Left rear door bezel LED
    • Left rear door switch LED
    • Driver seat LED
    • Console floor lamp
    • Front passenger seat LED
    • Security LEDs
    • RH hush LED
    • RH light pipe LED
  3. Ignition ON, with a scan tool clear the DTC and operate the vehicle within the conditions for running the DTC and verify the DTC does not reset.
  4. If DTC B2625 00 sets as current, test the LED indicator dimming control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  5. Reconnect each component one at a time and verify that the DTC does not reset as current after each component is reconnected.
  6. If the DTC sets as current, test or replace the component responsible for setting the DTC.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Luminescent Lamp Replacement - Driver or Passenger Seat
    •  Door Lamp Replacement
    •  Instrument Panel Flood Lamp Replacement - Left Side
    •  Instrument Panel Flood Lamp Replacement - Right Side
    •  Control Module References for BCM replacement, setup, and programming