B2622

DTC B2622 or B2623

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 B2622
- Dimming Display Pulse Width Modulation (PWM) Input Circuit Low

DTC B2623
- Dimming Display Pulse Width Modulation (PWM) Input Circuit High

Circuit/System Description

The body control module (BCM) receives a variable voltage signal from the instrument panel (I/P) dimmer switch requesting to illuminate the I/P controls illumination lamps to a desired intensity. When this occurs, the BCM directly sends a variable voltage based on the I/P dimmer switch position through the I/P lamps supply voltage circuit to the I/P controls illumination lamps.

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

B2622

When the BCM receives an I/P controls illumination lamp request signal and the I/P lamps supply voltage circuit is shorted to ground.

B2623

When the BCM is not receiving an I/P controls illumination lamp request signal and the I/P lamps supply voltage circuit is shorted to voltage.

Action Taken When the DTC Sets

The I/P controls illumination lamps will not operate or are always on.

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

1. Ignition ON, operate the parklamp switch to the ON position.
2. Verify that the instrument panel backlighting dims and goes to full brightness while operating the dimmer switch to dim and full bright.

• If the instrument panel backlighting lamps do not turn on or remain always on perform the IP Backlighting Lamp Control Circuit Test.

Circuit/System Testing

1. Ignition OFF, disconnect the BCM connector X2.
2. Ignition ON, verify that the following components backlighting is not illuminated.

* Accessory switch
* Hazard switch
* HVAC control module terminal
* Rear window wiper/washer switch
* Radio
* Sunroof switch
* Headlamp switch

• If any of the listed components backlighting is illuminated, test the associated control circuit for a short to voltage.

3. Connect a fused jumper wire from battery voltage to the following terminals and verify associated backlighting operation.

* Accessory switch A27
* Hazard switch A28
* HVAC control module terminal A29
* Rear window wiper/washer switch A30
* Radio A33
* Sunroof switch A34
* Headlamp switch A36

• If the jumper fuse opens while connected to any of the listed terminals, test the associated control circuit for a short to ground.

4. If all circuits test normal, replace the BCM.

Repair Instructions

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

Control Module References (Programming and Relearning)for BCM replacement, programming, and setup.