Stop Lamps Malfunction
Stop Lamps Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position. Ground for the left rear stop lamps is provided at G400. Ground for the right rear stop lamps is provided by G402.
Diagnostic Aids
Important: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation.
Circuit/System Testing
Stop Lamps Malfunction
1. Ignition OFF, disconnect harness connector at the inoperative stop lamp.
2. Test for less than 1.0 ohm of resistance between the ground circuit and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the stop lamp supply voltage circuit and ground.
4. Command the inoperative stop lamp ON and OFF with a scan tool. 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 circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, replace the inoperative stop lamp.
High Mounted Stop Lamp Malfunction
1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Test for less than 1.0 ohm of resistance between the ground circuit terminal B and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the stop lamp switch signal circuit terminal A and ground circuit terminal B.
4. Ignition ON, apply the brake pedal ON and OFF. The test lamp should turn ON and OFF as the brake pedal is applied and released.
• If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
• If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, replace the CHMSL.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
* High Mounted Stop Lamp Replacement
* Tail Lamp Replacement
* Tail Lamp Bulb Replacement
* Control Module References for BCM replacement, setup, and programming Programming and Relearning