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.

### Circuit/System Description

The instrument cluster turns ON the brake warning indicator for 5 s after ignition ON. The body control module (BCM) monitors the parking brake switch and will request the instrument cluster via serial data to turn the brake warning indicator ON when the parking brake is applied. When the electronic brake control module (EBCM) detects a fault, it sends a serial data message to the instrument cluster commanding the indicator ON.

### Reference Information

#### Schematic Reference

Hydraulic Brake Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Hydraulic Brake System 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

1. Ignition ON, with a scan tool command the instrument cluster All Indicators test ON and OFF. Verify the brake warning indicator turns ON and OFF.

⇒ | If the brake warning indicator does not turn ON and OFF, replace the P16 Instrument Panel Cluster (IPC).

2. Observe the scan tool BCM Park Brake Switch parameter while applying and releasing the parking brake. Verify the reading changes between Active and Inactive.

⇒ | If the parameter does not change between the specified values, refer to Circuit/System Testing.

3. Apply the parking brake. Verify the brake warning indicator turns ON.

⇒ | If the brake warning indicator does not turn ON, replace the K9 Body Control Module (BCM).

4. Release the parking brake. Verify the brake warning indicator turns OFF.

⇒ | If the brake warning indicator does not turn OFF, K17 Electronic Brake Control Module (EBCM).

### Circuit/System Testing

Note: Circuit/System Verification must be performed before Circuit/System Testing.

1. Ignition OFF, disconnect the harness connector at the B80 Park Brake Switch.
2. Inspect the B80 Park Brake Switch for physical damage and correct installation.

⇒ | If physical damage or incorrect installation is diagnosed, repair or replace the B80 Park Brake Switch.

3. Ignition ON, verify the scan tool BCM Park Brake Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the K9 Body Control Module (BCM).

4. Install a 3 A fused jumper wire between the signal circuit terminal 1 and ground.
5. Verify the scan tool BCM Park Brake Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).

6. If all circuits test normal, test or replace the B80 Park Brake Switch.

### Component Testing

#### Static Test

1. Ignition OFF, disconnect the harness connector at the B80 Park Brake Switch.
2. Test for infinite resistance between the signal circuit terminal 1 and the ground circuit terminal 2 with the parking brake released.

⇒ | If less than the specified value, replace the B80 Park Brake Switch.

3. Test for less than 5 Ω between the signal circuit terminal 1 and the ground circuit terminal 2 with the park brake applied.

⇒ | If greater than the specified value, replace the B80 Park Brake Switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Parking Brake Indicator Switch Replacement

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