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 STOP fuse in the underhood fuse block supplies battery voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery voltage is supplied to the electronic brake control module (EBCM), powertrain control module (PCM), left and right stop lamps, and the center high mounted stop lamp (CHMSL).

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

Ignition ON, observe the stop lamps while pressing and releasing the brake pedal. The stop lamps should turn on and off.

If not refer to the stop lamp circuit test.

Circuit/System Testing

Stop Lamp Circuit Test
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Ignition ON, verify that a test lamp illuminates 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. If the circuit tests normal and the B+ circuit fuse is open, test the signal circuit terminal 2 for a short to ground.

3. Connect the harness connector at the stop lamp switch.
4. Disconnect the harness connector at an affected stop lamp.
5. Test for less than 5 ohms between the listed ground circuit terminal and ground.

* Left or right stop lamp terminal G
* CHMSL terminal B

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

6. Verify that a test lamp does not illuminate between the stop lamp control circuit terminal A and ground.

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

7. Verify that the test lamp illuminates when the brake pedal is pressed.

• If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal replace the stop lamp switch.

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

Repair Instructions

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

* Tail Lamp Bulb Replacement (Service and Repair)
* Stop Lamp Switch Replacement (Service and Repair)
* High Mount Stop Lamp Replacement (Service and Repair)