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.
Diagnostic Fault Information
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). The stop and CHMSL lamps are grounded at all times at G105.
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 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 the inoperative stop lamp.
5. Test for less than 5 ohms between the listed ground circuit terminal and ground.
* Left or Right stop lamp terminal G
* Left or Right CHMSL terminal B
• If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between the control circuit terminal A and ground. Press and release the brake pedal. The test lamp should turn ON and OFF.
• If the test lamp is always ON, test the control circuit terminal for a short to voltage.
• If the test lamp is always OFF, test the control circuit terminal for a short to ground or an open/high resistance.
7. If all circuits test normal, replace the inoperative 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)