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

The STOP fuse in the engine wiring harness junction block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the VEHICLE STOP fuse and the VEHICLE CHMSL fuse. The current flow is now to the stop lamps which are grounded at G401 and G402. The center high mounted stop lamp (CHMSL) is grounded at G401.

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 (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 (Programming and Relearning)for scan tool information

Circuit/System Verification

Press and release the brake pedal while observing brake lamp operation.

If all of the brake lamps are always on or inoperative, refer to the Stop Lamp Switch Malfunction.
If 1 or 2 of the brake lamps function normally, refer to the Stop Lamp Malfunction.

Circuit/System Testing

Stop Lamp Switch Malfunction
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Test for less than 5.0 ohms between the low reference circuit terminal A.

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

3. Verify that a test lamp illuminates between the B+ circuit terminal B 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 stop lamp control circuit terminal A for a short to ground.

4. Install a 25A fused jumper wire between the stop lamp control circuit terminal A and the B+ circuit terminal B. Verify the stop lamps are illuminated.

• If the stop lamps are not illuminated, test the stop lamp control circuit for a short to ground or an open/high resistance.

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

Stop Lamp Malfunction
1. Ignition OFF, remove the fuse of the inoperative STOP/CHMSL lamp and inspect.

• If the fuse is OPEN, test the appropriate control circuit of the blown fuse for a short to ground.

2. Ignition OFF, disconnect the harness connector at the inoperative stop lamp.
3. Test for less than 5.0 ohms between the listed ground circuit terminal and ground.

* Center High Mounted Stop Lamp terminal B
* Tail/Stop Lamp terminal GRD

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

4. Connect a test lamp between the listed stop lamp control circuit terminal and ground.

* Center High Mounted Stop Lamp terminal A
* Tail/Stop Lamp terminal MJR

5. Press and release the brake pedal. The test lamp should turn ON and OFF when changing between the commanded states.

• If the test lamp is always ON, test the control circuit for a short to voltage.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.

6. If all circuits test normal, test or replace the inoperative stop lamp.

Repair Instructions

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

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