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: Brake Switch Circuit Malfunction
DTC C0161 71: Brake Switch Invalid Signal

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Antilock Brake System (ABS) Brake Switch/Sensor Circuit | C0161 00 | C0161 00 | C0161 00 | -

### Circuit/System Description

The brake switch informs the electronic brake control module (EBCM) when the brake is depressed. The brake switch is normally closed, supplying 12 volts to the EBCM when the brake is released. When the brake pedal is pressed, voltage on the torque converter clutch (TCC) brake switch signal circuit is 0 volts.

### Conditions for Running the DTC

• | The ignition is ON.

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

• | The ignition voltage is greater than 8 volts.

### Conditions for Setting the DTC

#### DTC C0161

• | 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 Antilock Brake System (ABS)/Traction Control System (TCS)/Electronic Stability Control (ESP)/Electronic Brake Distribution (EBD) for the duration of the ignition cycle.

• | The multi function display (MFD) displays the ABS Fault message.

• | The multi function display (MFD) displays the Traction Ctrl Off message.

• | The multi function display (MFD) displays the Stability Ctrl Off message.

### Conditions for Clearing the DTC

• | The condition for setting 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.

• | The DTC can be cleared using a scan tool.

### Diagnostic Aids

The DTC C0161 00 can be set if the vehicle has been driven with the brake applied during acceleration.

### Reference Information

#### Schematic Reference

Antilock Brake System Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

With scan tool installed, clear the DTCs then drive the vehicle in a straight line at a speed greater than 20 km/h (13 mph). If the DTC did not set as a current DTC see diagnostic aids.

### Circuit/System Testing

Important: If DTC B3445 is set to current diagnose it first. Refer to DTC B3445 .

1. Apply and release brake pedal. Verify brake lamps operate correctly. If brake lamps do not operate correctly, refer to Symptoms - Lighting Systems .
2. Test the stop lamp supply voltage circuit for a short to voltage, short to ground, an open or high resistance.

⇒ | If the stop lamp circuit tests normal, replace the brake modulator assembly/EBCM.

### Repair Instructions

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

• | Brake Pressure Modulator Valve Assembly Replacement

• | Electronic Brake Control Module Replacement

• | Control Module References