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 Descriptors

DTC C0161 00: Antilock Brake System Brake Switch Circuit
DTC C0161 71: Antilock Brake System Invalid Serial Data Received

### Circuit/System Description

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

### Conditions for Running the DTC

• | Ignition ON.

• | The vehicle speed is greater than 16 km/h (10 mph).

• | The ignition voltage is greater than 10 volts.

### Conditions for Setting the DTC

• | The brake pedal is sensed as applied.

• | The vehicle speed is greater than 40 km/h (25 mph).

• | The vehicles acceleration exceeds 8 km/h per second (5 mph per second).

• | Brake pedal is not applied.

• | Master cylinder pressure is greater than 150 psi.

• | The vehicle speed is greater than 24 km/h (14 mph).

• | The vehicles deceleration exceeds 11.5 km/h per second (7 mph per second).

### Action Taken When the DTC Sets

• | The EBCM disables the ABS/traction control system (TCS)/vehicle stability enhancement system (VSES) for the duration of the ignition cycle.

• | A DIC message and/or a warning indicator may be displayed.

### Conditions for Clearing the DTC

• | The condition for setting the DTC is no longer present.

• | The EBCM clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

### 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. Apply and release brake pedal. Verify brake lamps operate properly.

⇒ | If brake lamps do not operate properly, refer to Symptoms - Lighting.

2. Ignition ON, observe the scan tool EBCM BPP signal parameter while applying and releasing the brake pedal. The reading should change between Applied and Released.

⇒ | If the parameter does not change between applied and release, replace the EBCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM replacement, setup, and programming