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: Stop Lamp Switch Circuit Open

### Circuit/System Description

When the brake pedal is depressed, the contacts on the brake light switch close to illuminate the brake lights. Battery voltage is also applied to terminal 14 of the electronic brake control module (EBCM), which signals the antilock brake system (ABS) controller that the brakes are applied and ABS may be needed. Without this, signals from a wheel speed sensor that may indicate a need for ABS intervention are questionable. When the brake pedal is not depressed, the EBCM terminal 14 is grounded through the brake lights.

This procedure will check whether there is no output or constant output from the brake light switch and will determine the cause as a faulty switch or a problem in the circuitry.

### Conditions for Running the DTC

• | Vehicle speed is greater than 6 km/h (4 mph) with the brake pedal not applied.

| OR

• | Vehicle speed is greater than 15 km/h (9 mph) and the brake pedal is actuated.

### Conditions for Setting the DTC

• | The ground connection or the positive connection at the EBCM has failed.

• | There is an open, short to ground, or short to positive in the vehicle wiring.

• | The brake light switch has failed.

### Action Taken When the DTC Sets

The system records a DTC C0161.

### Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

### 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

Verify the brake lamps operate.

⇒ | If brake lamps do not operate, refer to appropriate diagnosis.

### Circuit/System Testing

1. Ignition OFF, disconnect the EBCM connector.
2. Ignition ON, check for 10-16V between the EBCM terminal 16 and ground with brake pedal applied.

⇒ | If the voltage is not as specified, test the circuit for a short to ground or an open/high resistance.

3. Ignition ON, check for 11-14V between the B+ circuit and ground.

⇒ | If the voltage is not as specified, test the B+ circuit for a short to ground or an open/high resistance.

4. Test for less than 1 ohm between the ground circuit and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the BPMV/EBCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM replacement, setup, and programming