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.

### DTC Descriptor

DTC C0161 5A: Antilock Braking System Brake Switch Circuit Not Plausible

### Circuit/System Description

The body control module (BCM) monitors the brake pedal position sensor and sends a serial data message when the brake pedal is applied. When the vehicle is stopping, the electronic brake control module (EBCM) monitors for the brake pedal applied serial data message from the BCM, with the brake pressure increasing and the vehicle slowing down, or when the vehicle is accelerating, the brake pedal is not applied and brake pressure is not increasing.

### Conditions for Running the DTC

Ignition ON.

### Conditions for Setting the DTC

• | The EBCM detects 4 accelerations from standstill to a vehicle speed greater 40 km/h (26 MPH) without any brake light switch signal changes.

• | The EBCM detects the vehicle speed is greater than 20 km/h (13 MPH), the brake pedal is applied for 360 s, and brake pressure is less than 15 bar (218 PSI).

### Conditions for Clearing the DTC

A current DTC clears when the diagnostic runs and passes.

### Diagnostic Aids

The DTC C0161 5A can be set if the brake pedal is applied while accelerating or the brake pedal position sensor is out of adjustment.

### Reference Information

#### Schematic Reference

Antilock Brake System Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

ABS 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 stop lamps while applying and releasing the brake pedal. Verify the stop lamps operate properly.

⇒ | If the stop lamps do not operate properly, refer to Symptoms - Lighting

### Circuit/System Testing

Replace the K17 Electronic Brake Control Module (EBCM) and verify the DTC does not reset.

⇒ | If the DTC resets replace the K9 Body Control Module (BCM).

### Repair Instructions

• | Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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