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: ABS/TCS Brake Switch Circuit

### Circuit/System Description

The body control module (BCM) illuminates the stop lamps by applying battery positive voltage to the stop lamp supply voltage circuit. The electronic brake control module (EBCM) receives a voltage input from the stop lamp supply voltage circuit to determine if the brake pedal is applied.

### Conditions for Running the DTC

• | The ignition is ON.

• | The vehicle speed is greater than 20 km/h (12 mph).

### Conditions for Setting the DTC

• | The brake pedal is sensed as applied for 6 minutes.

• | The vehicle speed is greater than 20 km/h (12 mph).

• | The EBCM does not receive a signal change from the stop lamp supply voltage circuit.

• | Vehicle speed exceeds 40 km/h (25 mph) in four cycles, and decelerates to under 3 km/h (2 mph).

### Action Taken When the DTC Sets

The ABS remains functional.

### Conditions for Clearing the DTC

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

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

### Diagnostic Aids

The DTC C0161 can be set if the vehicle has been driven with the brake applied during acceleration. Also inspect the brake pedal switch and connector for proper operation.

### 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 scan tool EBCM Stop Lamp parameter. The reading should be Released and change between Applied and Released when pressing and releasing the brake pedal, the stop lamps should turn on and off.

⇒ | If not within the specified value, refer to Stop Lamps Malfunction. If the circuits test normal, replace the EBCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM replacement, setup and programming