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.
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 (Wiring Diagram Index)
Connector End View Reference
Component Connector End Views (Component Connector End 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 (Control Module References)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 circuit test.
If 1 or 2 of the brake lamps function normally, refer to the stop lamp circuit test.
Circuit/System Testing
Stop Lamp Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the stop lamp switch.
2. Verify that a test lap illuminates between the battery supply circuit terminal B and ground.
• If the test lamp does not illuminate, test the battery supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the battery supply circuit fuse is open, test the stop lamp control circuit terminal A for a short to ground.
3. Verify that the stop lamps are not illuminated.
• If any of the stop lamps are illuminated, test the stop lamp control circuit for a short to voltage.
4. Install a 25A fused jumper wire between the stop lamp control circuit terminal A and the battery supply circuit terminal B. Verify the stop lamps are illuminated.
• If the stop lamps are not illuminated test the stop lamp control circuit for an open/high resistance.
5. If all circuits test normal replace the stop lamp switch.
Stop Lamp Circuit Test
1. Ignition OFF, disconnect the harness connector at the affected stop lamp.
2. Test for less than 1 ohm of resistance between the listed ground circuit terminal and ground.
* Center high mounted stop lamp terminal B
* Tail lamp terminal GRD
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the listed stop lamp control circuit terminal and ground circuit terminal.
* Center high mounted stop lamp terminal A to B
* Tail lamp terminal MJR to GRD
4. 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.
5. If all circuits test normal, test or replace the affected stop lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Tail Lamp Assembly and /or Backup, Sidemarker, Stop, Turn Signal Bulb Replacement (Service and Repair)
* High Mount Stop Lamp Replacement (Service and Repair)
* Stop Lamp Switch Replacement (Service and Repair)