B2620

DTC B2620

Diagnostic Instructions

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

DTC Descriptor

DTC B2620
- Display Dimming Pulse Width Modulation (PWM) Input Circuit

Diagnostic Fault Information






Circuit/System Description

The body control module (BCM) directly sends a 5-volt reference voltage to the instrument panel (I/P) dimmer switch which is then adjusted based on the I/P dimmer switch position and returned as a low reference and a signal to the BCM. The BCM uses this signal to directly control the desired level of instrument panel illumination lamp intensity.

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.

Circuit/System Verification

Ignition ON, observe the scan tool dimming input parameter. The reading should change between high and low while rotating the IP dimmer switch.

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 after completing the diagnostic procedure. Verification Tests

* Headlamp Switch Replacement