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

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5 V Reference | C0277 06 | C0277 06 | -- | --
Signal | C0277 06 | C0277 06 | C0277 07 | C0277 09
Low Reference | -- | C0277 06 | -- | --

### 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.

• | DTC C0131 is not present.

### Conditions for Setting the DTC

• | The EBCM detects brake pedal is not applied and the brake pressure is greater 15 bar (218 PSI) for 2 s.

• | The EBCM detects the vehicle speed is greater than 16 km/h (10 MPH), the brake pedal is applied for 122 s, and brake pressure is less than 6.2 bar (90 PSI).

### Action Taken When the DTC Sets

The EBCM disables the hill start assist for the duration of the ignition cycle.

### Conditions for Clearing the DTC

• | A current DTC clears when the diagnostic runs and passes.

• | The EBCM will turn OFF the indicator in the next ignition cycle.

### 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

1. Ignition ON, verify that DTC C0277 is not present in the BCM.

⇒ | If DTC C0277 is present, refer to LINK to diagnose that DTC prior to this diagnostic.

2. 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

1. 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