Stop Lamps Malfunction

Stop Lamps Malfunction

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.

Diagnostic Fault Information





Circuit/System Description

Battery voltage is supplied to the STOP lamp fuse and Stop Lamp Switch at all times. When the driver presses the brake pedal, the switch contacts close and B+ is supplied to the body control module (BCM), electronic brake control module (EBCM), powertrain control module (PCM), and the Center High Mounted Stop Lamp (CHMSL). Ground is supplied at all times to the Tail/Stop Lamp and CHMSL.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
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 Testing

Stop Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Connect a test lamp between the B+ circuit terminal 1 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Connect a test lamp between the control circuit terminal 2 and ground.

• If the test lamp illuminates, test the circuit for a short to voltage.

4. Ignition OFF, disconnect the harness connector at the inoperative tail/stop lamp or CHMSL.
5. Test for less than 5 ohms between the ground circuit terminals listed below and ground.

* Tail/Stop Lamp terminal G
* CHMSL terminal 1

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

6. Connect a 15A fused jumper wire between the stop lamp switch B+ circuit terminal 1 and the stop lamp switch control circuit terminal 2.
7. Connect a test lamp between the control circuit terminal of the inoperative lamp listed below and ground.

* Tail/Stop Lamp terminal B
* CHMSL terminal 2

• If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance.

8. If all circuits test normal, replace the stop lamp switch.

Repair Instructions

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

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