B2620
DTC B2620
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 B2620 00
- Display Dimming Pulse Width Modulation (PWM) Input Circuit
Diagnostic Fault Information
Circuit/System Description
When the ignition switch is turned to the RUN position, the radio's VF displays turn ON at maximum brightness. When the park lamps are ON, all incandescent back lighting turn ON at the dimming level indicated by the instrument panel (I/P) dimmer switch. At the same time all VF displays dim to match the indicated dimming level. The panel dimmer switch potentiometer is an input to the body control module (BCM). When the driver selects a dimming setting by moving the I/P dimming switch potentiometer, all incandescent back lighting lamps are provided with a specific voltage. The incandescent back lighting lamps are then grounded at G201, G302, and G303. When the I/P dimmer switch is moved from MIN to MAX, all vacuum fluorescent (VF) displays, as well as all incandescent back lighting respond from minimum intensity to maximum brightness in response to the I/P dimmer switch.
Conditions for Running the DTC
The battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
* The dimmer switch 5-volt reference is greater than 6.15 volts.
* The dimmer switch 5-volt reference is less than 3.85 volts.
* The dimmer switch signal circuit is greater than 4.83 volts.
Action Taken When the DTC Sets
The interior dimming backlights and indicators are inoperative or at full intensity whenever 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 Schematics)
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 Testing
1. Ignition OFF, disconnect the harness connector X1 at the headlamp switch.
2. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and ground.
• If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
• If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the BCM.
3. Verify the scan tool Dimming Input parameter is less than 1.0 volt.
• If greater than the specified range, test the signal circuit terminal G for a short to voltage. If the circuit tests normal, replace the BCM.
4. Install a 3A fused jumper wire between the signal circuit terminal G and the 5-volt reference circuit terminal A. Verify the scan tool Dimming Input parameter is greater than 4.5 volts.
• If less than the specified range, test the signal circuit for short to ground 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