Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Brake Pedal Position Sensor Signal | C0277 06 | C0277 06 | C0277 07 | C0277 09 |
Brake Pedal Position Sensor 5-Volt Reference | C0277 06, C0870 03 | C0277 06 | 1 | -- |
Center High Mounted Stop Lamp (CHMSL) Control | 2 | 2 | 2 | -- |
Brake Pedal Position Sensor Low Reference | -- | C0277 07 | 1 | -- |
Left Rear Stop/Turn Lamp Control | 1 | 1 | 1 | -- |
Right Rear Stop/Turn Lamp Control | 1 | 1 | 1 | -- |
Center High Mounted Stop Lamp (CHMSL) Ground | -- | 2 | 1 | -- |
Left Rear Stop/Turn Lamp Ground | -- | 1 | 1 | -- |
Right Rear Stop/Turn Lamp Ground | -- | 1 | 1 | -- |
1. Stop Lamps Malfunction 2. Center High Mounted Stop Lamp (CHMSL) Malfunction | ||||
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, transmission control module (TCM), engine control module (ECM), and stop lamp relay coil side. When the stop lamp relay receives battery voltage from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the STOP LP fuse to illuminate the center high mounted stop lamp (CHMSL).
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, observe the scan tool Brake Lamp Cmd. parameter as you apply and unapply the brake pedal. The reading should cycle between OFF and ON as the brake pedal is applied and released.
- With a scan tool, command the LR Stop/Turn Signal Lamp ON and OFF. The LR turn signal should turn ON and OFF when changing between the commanded states.
- With a scan tool, command the RR Stop/Turn Signal Lamp ON and OFF. The RR turn signal should turn ON and OFF when changing between the commanded states.
| ⇒ | If the reading does not change as the brake pedal is applied and released, refer to Brake Pedal Position Sensor (BPPS) Malfunction. |
| ⇒ | If the LR stop lamp does not illuminate when commanded, refer to Stop Lamps Malfunction. |
| ⇒ | If the RR stop lamp does not illuminate when commanded, refer to Stop Lamps Malfunction. |
Circuit/System Testing
Stop Lamps Malfunction
- Ignition OFF, disconnect the harness connector at the inoperative stop lamp.
- Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal G and ground.
- Connect a test lamp between the control circuit terminal A and ground.
- Ignition ON, command the appropriate Stop/Turn Signal Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, replace the inoperative tail lamp assembly.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | 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. |
Center High Mounted Stop Lamp (CHMSL) Malfunction
- Ignition OFF, disconnect the harness connector at the CHMSL.
- Ignition OFF, exterior lamps OFF, test for less than 5.0 ohms between the ground circuit terminal B and ground.
- Connect a test lamp between the control circuit terminal A and ground.
- Ignition ON, command the stop lamps ON and OFF by applying and releasing the brake pedal. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the CHMSL.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | 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. |
Brake Pedal Position Sensor (BPPS) Malfunction
- Ignition OFF, disconnect the harness connector at the BPPS.
- Ignition ON, verify that a test lamp does not illuminate between the low reference circuit terminal C and ground.
- Ignition ON, test for 4.8 volts and 5.2 volts between the 5-volt reference circuit terminal A and ground.
- If all circuits test normal, replace the BPPS.
| ⇒ | If the test lamp illuminates, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
| ⇒ | If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM. |
| ⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the BCM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for BCM replacement, setup, and programming |
