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, transmission control module (TCM), engine control module (ECM), and stop lamp relay coil. The BCM also supplies the stop lamp relay coil with ground. When the stop lamp relay receives battery voltage and ground from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage to the center high mounted stop lamp (CHMSL). Ground for the left stop lamp and CHMSL are provided at G301 and the right stop lamp receives ground at G302.

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.

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Stop Lamps Malfunction (North America)

1. Ignition OFF, disconnect harness connector at the inoperative stop lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal D and ground.

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

3. Connect a test lamp between the control circuit terminal E and the ground circuit terminal D.
4. Command the Stop Lamp Relay Control 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.

Stop Lamps Malfunction (European)

1. Ignition OFF, disconnect the stop lamp relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal E3 and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

3. Verify that a test lamp illuminates between the B+ circuit terminal C2 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 control circuit terminal E3 for a short to ground. If the circuit tests normal, test or replace the stop lamp relay.

4. Disconnect harness connector at the inoperative stop lamp.
5. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal D and ground.

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

6. Connect the harness connector at the inoperative stop lamp.
7. Connect a 15A fused jumper wire between the B+ circuit terminal C2 and the control circuit terminal E3. Verify the stop lamps are activated.

⇒	If the stop lamps are not activated, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the inoperative stop lamp.

8. Connect a test lamp between the signal circuit terminal C3 and the control circuit terminal E2.
9. Command the Stop Lamp Relay Control 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 ground. If the circuit tests normal, replace the BCM.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

10. If all circuits test normal, test or replace the stop lamp relay.

High Mounted Stop Lamp Malfunction

1. Ignition OFF, disconnect the stop lamp relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal E3 and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

3. Verify that a test lamp illuminates between the B+ circuit terminal C2 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 control circuit terminal E3 for a short to ground. If the circuit tests normal, test or replace the stop lamp relay.

4. Disconnect harness connector at the CHMSL.
5. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal B and ground.

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

6. Connect the harness connector at the CHMSL.
7. Connect a 15A fused jumper wire between the B+ circuit terminal C2 and the control circuit terminal E3. Verify the CHMSL is activated.

⇒	If the CHMSL does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the CHMSL.

8. Connect a test lamp between the signal circuit terminal C3 and the control circuit terminal E2.
9. Command the Stop Lamp Relay Control 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 ground. If the circuit tests normal, replace the BCM.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

10. If all circuits test normal, test or replace the stop lamp relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.