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 stop/tail lamp assembly is provided by G402 and ground for the right stop/tail lamp assembly is provided by G403.

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

Lighting Systems Connector End Views

Electrical Information Reference

Scan Tool Reference

Stop Lamps Circuit Test

1. Ignition OFF, disconnect the (C4) harness connector at the BCM.
2. Ignition ON, verify a test lamp illuminates between the following B+ terminals and ground.

•	B+ terminal 1

•	B+ terminal 2

•	B+ terminal 4

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the B+ circuit and the respective stop lamp circuits for a short to ground.

3. Ignition OFF, disconnect the harness connector at the brake pedal position sensor.
4. Verify that a test lamp illuminates between the low reference circuit terminal C and B+.

⇒	If the test lamp does not illuminate, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

5. Ignition OFF, disconnect harness connector at the inoperative stop/turn lamp.
6. Ignition OFF, test for less than 5.0 ohms of resistance between the ground circuit terminal G and ground.

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

7. Connect a test lamp between the supply voltage circuit terminal A and ground.
8. Ignition ON, command the appropriate BCM LR or RR Turn Signal 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 supply voltage circuit for a short to voltage. If the circuit tests normal, replace the BCM.

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

9. If all circuits test normal, replace the inoperative stop/turn signal lamp assembly.

High Mounted Stop Lamp Circuit Test

1. Ignition OFF, disconnect the harness connector at the CHMSL.
2. Ignition OFF, test for less than 5.0 ohms 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 supply voltage circuit terminal A and the ground circuit terminal B.
4. Ignition ON, apply and release the brake pedal. The test lamp should turn ON and OFF as the brake pedal is applied and released.

⇒	If the test lamp is always ON, test the supply voltage circuit for a short to voltage. If the circuit tests normal, replace the BCM.

⇒	If the test lamp is always OFF, test the supply voltage 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 CHMSL.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.