B2624

DTC B2624

Diagnostic Instructions

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

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

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

When the BCM monitors a signal voltage equal to or greater than 4.86 volts for more than one second.

Action Taken When the DTC Sets

The I/P illumination lamp dimming will not operate.

Conditions for Clearing the DTC

* This DTC will clear on current status after the condition for setting the fault is corrected.
* A history DTC will clear after 100 consecutive ignition cycles without a fault present.

Reference Information
Schematic Reference

Interior Lights Dimming Schematics (Interior Lights Dimming Diagrams)
Connector End View Reference

Component Connector End Views (Connector 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 Verification

Ignition ON, observe the scan tool dimming potentiometer while turning the dimmer switch from dim to bright. The reading should change between 0.6 to 4.5 volts.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for less than 5 ohms between the ground circuit terminal 3 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool dimming potentiometer is greater than 4.5 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 the ground circuit terminal 3. Verify the scan tool dimming potentiometer is less than 0.6 volts.

• 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.

Component Testing

1. Ignition OFF, disconnect the harness connector at the headlamp switch.
2. Test for 500-4.5k ohms between the signal terminal 14 and the low reference terminal 3 while turning the dimmer switch from dim to bright.

• If not the specified value, 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, setup, and programming