Stop Lamps Malfunction

Stop Lamps Malfunction

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

Circuit/System Description

The BCM controls the stop lamps based on the input from the Brake Pedal Position Sensor (BPPS). When the BCM detects the brake pedal is depressed, B+ is applied to the stop lamp switch signal circuit and both stop/turn lamp supply voltage circuits, illuminating the center high mount stop lamp (CHMSL) and both stop lamps.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior 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, verify DTC C0277, C0278, C0283, or C0870 is not set.

• If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions).

2. With the brake pedal depressed, verify the stop lamps and CHMSL are illuminated.

• If the CHMSL does not illuminate, refer to CHMSL Circuit Malfunction.

• If one or more of the stop lamps do not illuminate, refer to Stop Lamp Circuit Malfunction.

Circuit/System Testing

CHMSL Circuit Malfunction
1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Test for less than 10 ohms of resistance between the ground circuit terminal B and ground.

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

3. Install a test lamp between the signal circuit terminal A and ground.
4. Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.

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

Stop Lamp Circuit Malfunction
1. Ignition OFF, disconnect the harness connector at the appropriate stop lamp bulb.
2. Test for less than 10 ohms of resistance between the ground circuit terminal G and ground.

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

3. Install a test lamp between the control circuit terminal A and ground.
4. Ignition ON, verify the test lamp turns ON and OFF when pressing and releasing the brake pedal.

• 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, test or replace the appropriate stop lamp bulb.

Repair Instructions

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

* High Mount Stop Lamp Replacement (Service and Repair)
* License Lamp Bulb Replacement (Service and Repair)
* Control Module References (Programming and Relearning)for BCM replacement, setup, and programming