B2624

DTC B2624

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.



DTC Descriptor
DTC B2624
- Dimming Display Pulse Width Modulation (PWM) Input Circuit Open




Diagnostic Fault Information






Circuit/System Description

The body control module (BCM) directly sends a reference voltage to the instrument panel (I/P) dimmer switch which is then reduced based on the I/P dimmer switch position and monitored as a signal to the BCM. The BCM uses this signal to directly control the desired level of I/P illumination lamp intensity.


Conditions for Running the DTC

The battery voltage must be between 9-16 volts.


Conditions for Setting the DTC

* The BCM detects a short to voltage or an open/high resistance in the I/P dimmer switch signal circuit.
* The BCM detects a short to voltage in the I/P dimmer switch voltage reference circuit.



Action Taken When the DTC Sets

Interior backlighting will be inoperative or will not dim with the I/P dimmer switch depending on what fault is present.


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 (Interior Lights Dimming Schematics)
Connector End View Reference

Component Connector End Views (Component Connector End Views)
Description and Operation

Interior Lighting Systems Description and Operation (Interior Lighting Systems Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Ignition OFF, verify that a test lamp illuminates between B+ and the low reference circuit terminal 3.

• If the test lamp does not illuminate, test the low reference circuit for a short to ground or an open/high resistance.

3. Ignition ON, verify that the scan tool Dimming Potentiometer parameter is greater than 9.0 volts.

• If not the specified value, test the signal circuit terminal 14 for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal 14 and ground. Verify the scan tool Dimming Potentiometer is less than 1.0 volt.

• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the headlamp switch.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Headlamp Switch Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, programming, and setup