Buick Regal: DTC B2625

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 02

Display Dimming Pulse Width Modulation Output Circuit Short to Ground

Diagnostic Fault Information

1. Interior Backlighting Malfunction
2. Door Lock Indicator Malfunction

Circuit/System Description

The instrument panel dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The instrument panel dimmer switch provides a voltage signal to the body control module (BCM) that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The BCM provides a low reference, signal, and B+ voltage reference to the instrument panel dimmer switch. When the instrument panel dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the instrument panel dimmer switch through the instrument panel dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies a pulse width modulated voltage through the LED dimming 1 and dimming 2 control circuits illuminating the interior backlighting to the requested level of brightness.

Conditions for Running the DTC

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

Conditions for Setting the DTC

The BCM detects a short to ground in the LED backlight dimming control circuit terminal 5 X1.

Actions Taken When the DTC Sets

The LED backlight dimming control circuit driver is shut down.

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 Wiring Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

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 appropriate component listed below, ignition ON.

• A98 Front Overhead Console Assembly (-C3U)
• S13D Door Lock Switch - Driver
• S13P Door Lock Switch - Passenger
• S48E Multifunction Switch - Center Console (F45/UHX&UGN/UD5&UD7)

2. Place the interior backlighting dimmer switch in the HIGH position for high backlighting intensity.

3. Verify a test lamp illuminates between the appropriate control circuit terminal listed below and ground.

• A98 Front Overhead Console Assembly terminal 18 (-C3U)
• S13D Door Lock Switch - Driver terminal 5
• S13P Door Lock Switch - Passenger terminal 5
• S48E Multifunction Switch - Center Console terminal 3 (F45/UHX&UGN/UD5&UD7)
• If the test lamp does not illuminate

1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K9 Body Control Module.

• Go to next step: If the test lamp illuminates

4. Place the interior backlighting dimmer switch in the LOW position for low backlighting intensity.

5. Verify a test lamp does not illuminate at FULL intensity between the appropriate control circuit listed below and ground.

• A98 Front Overhead Console Assembly terminal 18 (-C3U)
• S13D Door Lock Switch - Driver terminal 5
• S13P Door Lock Switch - Passenger terminal 5
• S48E Multifunction Switch - Center Console terminal 3 (F45/UHX&UGN/UD5&UD7)
• If the test lamp illuminates at full intensity

1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K9 Body Control Module.

• Go to next step: If the test lamp does not illuminate at full intensity

6. Test or replace the component with the inoperative indicator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Door Lock Switch Replacement - Driver Side
• Door Lock Switch Replacement - Passenger Front
• Floor Console Accessory Function Switch Replacement
• Roof Console Replacement
• Control Module References for BCM replacement, programming, and setup

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