High Mounted Stop Lamp Inoperative

HIGH MOUNTED STOP LAMP INOPERATIVE




DIAGNOSTIC FAULT INFORMATION

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

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.

CIRCUIT/SYSTEM TESTING
1. Ignition OFF, disconnect the CHMSL harness connector.
2. Connect a test lamp between the CHMSL supply voltage circuit and ground.
3. Ignition ON, depress and hold the brake pedal. The test lamp should illuminate when the brakes are applied.
- If the test lamp does not illuminate, repair the CHMSL voltage supply circuit for a short to ground or an open/high resistance.
4. Verify that a test lamp illuminates between battery voltage and the CHMSL ground circuit.
- If the test lamp does not illuminate, repair the CHMSL ground circuit for an open/high resistance.
5. If all circuits test normal, replace the CHMSL.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

High Mounted Stop Lamp Bulb Replacement