For 1990-2009 cars

### 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
--- | --- | --- | --- | ---
BCM B+ Terminal 4 X4 | B3445 00 | B3445 00 | -- | --
Brake Pedal Position Sensor 5-Volt Reference | C0277 06, C0890 03, C0161 71 | C0277 06, C0161 71 | C0277 07, C0161 71 | --
Brake Applied Signal Terminal 6 X5 | C0297 00, P0571 00 | 3 | 3 | --
Brake Pedal Position Sensor Signal | C0277 06, C0161 71 | C0277 06, C0161 71 | C0277 07, C0161 71 | C0277 09
Stop Lamp Control | B3445 00 | 1 | 1 | --
Brake Position Sensor Low Reference | -- | 1 | 1 | --
Center High Mounted Stop Lamp (CHMSL) Ground | -- | 2 | -- | --
Left Rear Tail/Stop Lamp Ground | -- | 1 | -- | --
Right Rear Tail/Stop Lamp Ground | -- | 1 | -- | --
1. Stop Lamps Malfunction 2. Center High Mounted Stop Lamp (CHMSL) Malfunction 3. Cruise Control 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 (BPP) 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 voltage to the stop lamp control circuit illuminating the left and right stop lamps and the center high mounted stop lamp (CHMSL). The BCM also applies battery voltage to the transmission control module (TCM) and engine control module (ECM) via the brake applied signal circuit.

### Reference Information

#### 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

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

Ignition ON, observe the scan tool Brake Status parameter as you apply and unapply the brake pedal. The parameter should change between Off and On as the brake pedal is applied and released.

⇒ | If the parameter does not change as the brake pedal is applied and released, refer to Brake Pedal Position (BPP) Sensor Malfunction.

⇒ | If the parameter changes as the brake pedal is applied and released, refer to Stop Lamps Malfunction.

### Circuit/System Testing

#### Stop Lamps Malfunction

1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Verify that a test lamp illuminates between the B+ circuit terminal 4 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Connect the X4 harness connector at the BCM.
4. Disconnect the harness connector at the inoperative stop lamp.
5. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.

• | Tail/stop lamp terminal GRD

• | CHMSL terminal B

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

6. Connect a test lamp between the appropriate control circuit terminal listed below and ground.

• | Tail/stop lamp terminal MJR

• | CHMSL terminal A

7. Ignition ON, command the Brake Light Test 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.

8. If all circuits test normal, replace the inoperative stop lamp.

#### Brake Pedal Position (BPP) Sensor Malfunction

1. Ignition OFF, disconnect the harness connector at the BPP sensor.
2. Ignition ON, verify that a test lamp illuminates between B+ and the low reference circuit terminal C.

⇒ | If the test lamp does not illuminate, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

3. Ignition ON, test for 4.8 volts and 5.2 volts between the 5-volt reference circuit terminal A and ground.

⇒ | 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.

4. If all circuits test normal, test or replace the brake pedal position sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | High Mount Stop Lamp Replacement

• | Tail Lamp Assembly and /or Backup, Sidemarker, Stop, Turn Signal Bulb Replacement

• | Stop Lamp Switch Replacement

• | Control Module References for BCM replacement, setup, and programming