B3445

DTC B3445

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 B3445 00

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Stop Lamp Circuit

Diagnostic Fault Information






Circuit/System Description

The stop lamp switch is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides a low reference signal and a B+ reference voltage to the stop lamp switch. When the stop lamp switch contacts close indicating the brakes have been applied, the BCM will apply battery voltage to stop lamp relay control circuit and the center high mounted stop lamp (CHMSL). When the stop lamp relay receives battery voltage from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage to the STOP LP fuse to illuminate the left and right stop lamps.

Conditions for Running the DTC

* Battery voltage must be between 9-16 V.

* Brakes APPLIED.

Conditions for Setting the DTC

The BCM detects a short to ground in the CHMSL control circuit when the stop lamps are being commanded ON.

Actions Taken When the DTC Sets

The BCM will not illuminate the CHMSL.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.

* A history DTC will clear once 100 malfunction-free ignition cycles have occurred.

Diagnostic Aids

Note:
The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation Exterior Lighting Systems.

Reference Information

Schematic Reference

Exterior Lights Schematics Exterior Lights Schematics

Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)

Description and Operation

Exterior Lighting Systems Description and Operation Exterior 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

1. Ignition OFF, disconnect the harness connector at the CHMSL.

2. Test for less than 5.0 ohms between the ground circuit terminal B and ground.

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

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

4. Ignition ON, turn the stop lamps ON and OFF by applying and releasing the brake pedal. The test lamp should turn ON and OFF when changing between the selected states.

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

• 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.

5. If all circuits test normal, replace the CHMSL.

Repair Instructions

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

* Tail Lamp Bulb Replacement (Chevrolet) Service and RepairTail Lamp Bulb Replacement (GMC) Service and Repair

* Control Module References Control Module References for BCM replacement, setup, and programming