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 00: Antilock Brake System (ABS) Brake Switch Circuit

### Circuit/System Description

The electronic brake control module (EBCM) monitors the brake pressure sensor voltage, vehicle speed, and a serial data message from the BCM that the brake pedal is either Applied or Released. When the vehicle is stopping the EBCM detects the brake pressure sensor voltage increases and correlates the readings to the serial data message from the BCM the brake pedal is applied, and the vehicle is slowing down, or when the vehicle is accelerating, the brake pedal is Released and brake pressure sensor voltage returns to 0.

### Conditions for Running the DTC

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

• | The ignition voltage is greater than 9.5 volts.

• | No Brake pressure DTCs detected

### Conditions for Setting the DTC

• | The EBCM detects the vehicle speed greater than 21 km/h (13 mph), the brake pedal is Applied for 1 minute , and brake pressure sensor input voltage is at 0.

• | The EBCM detects the vehicle speed decreases, the brake pedal is Released and the brake pressure sensor input voltage increases.

### Action Taken When the DTC Sets

• | The EBCM disables the antilock brake system (ABS), traction control system (TCS) and 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 the DTC is no longer present.

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

### Diagnostic Aids

DTC C0161 00 can set if the vehicle accelerates with the brake applied.

### 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. Verify that DTC C0277 or C0890 is not set.

⇒ | If DTC is set, refer to DTC C0277 or C0890.

2. Ignition ON, observe the scan tool EBCM BPP Signal parameter. The reading should be Released and change between Applied and Released when pressing and releasing the brake pedal.

⇒ | If not within the specified value, perform the scan tool BCM BPP Sensor Calibration procedure. Refer to Brake Pedal Position Sensor Calibration. If the DTC resets, replace the BPP sensor.

3. Ignition ON, observe the scan tool EBCM Brake Pressure Sensor Input Voltage parameter. The reading should be 0 and change between 0-2 volts when pressing and releasing the brake pedal.

⇒ | If not within the specified value, perform the scan tool EBCM special functions Brake Pressure Sensor Calibration. If the DTC resets, replace the BPMV.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Brake Pressure Modulator Valve Replacement

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