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B2625




DTC B2625

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 B2625 02

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Display Dimming Pulse Width Modulation (PWM) Output Circuit Short to Ground

Diagnostic Fault Information






Circuit/System Description

When the headlamp switch is placed in either the HEAD or PARK position, ground is applied to the park lamp signal circuit to the body control module (BCM). The BCM responds by applying ground to the park lamp relay control circuit. This energizes the park lamp relay coil causing the relay switch contacts to close allowing battery voltage to flow to all of the park, tail, license, marker lamps, interior ambient lighting, and to the BCM. The BCM receives the voltage from the park lamp relay indicating the park lamps are ON. The BCM uses this signal to command the interior backlighting ON and OFF. The instrument panel (I/P) lamp dimmer switch is used to increase and decrease the brightness of the interior backlighting components. The I/P dimmer switch provides a voltage signal that will increase as the brightness of the lights are increased and decrease as the brightness of the lights are decreased. The body control module (BCM) provides a B+ voltage signal and a low reference to the I/P dimmer switch. When the I/P dimmer switch is placed in the desired position, the dimmed voltage setting is applied from the I/P dimmer switch through the I/P dimmer switch signal circuit to the BCM. The BCM interprets the signal and applies the dimmed voltage to the indicator dimming control circuit and the interior backlighting components dim to the requested level.

Conditions for Running the DTC

* Battery voltage must be between 9-16 V.

* Park lamps ON.

Conditions for Setting the DTC

The BCM detects a short to ground in the indicator dimming control circuit.

Actions Taken When the DTC Sets

The BCM will not illuminate the interior backlighting supplied by the indicator dimming control circuit.

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 5 Bow Lowered Switch (CM7)

Description and Operation

Interior Lighting Systems Description and Operation Interior Lighting Systems

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Testing

Note:
Each back lighted component may need to be disconnected to isolate a short to voltage or short to ground. Use the schematic to identify the following:

* Back lighted components the vehicle is equipped with.

* Component locations on the back lighting dimming control circuit.

* Each component's control and ground circuit terminals.

1. Ignition OFF, disconnect the harness connector at any component with inoperative backlighting.

2. Ignition OFF, scan tool disconnected, interior lamps OFF, doors CLOSED, test for less than 5 ohms between the ground circuit and ground.

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

3. Connect a test lamp between the control circuit and ground.

4. Command the Incandescent Dimming Control ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the component with the inoperative backlighting.

Repair Instructions

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

* Diagnostic Repair Verification Verification Tests

* Control Module References Control Module References for control module replacement, setup, and programming