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 C0055: Rear Wheel Speed Sensor Circuit
DTC C0055 5A: Rear Wheel Speed Sensor Circuit Erratic Signal

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Rear Wheel Speed Sensor Signal | C0055 | C0055 | C0055 | C0055 5A

### Circuit/System Description

The electronic control module (ECM) converts the data from the vehicle speed sensor to a 128K pulses/mile signal. The electronic brake control module (EBCM) uses the vehicle speed signal from the ECM in order to calculate the rear wheel speed.

### Conditions for Running the DTC

#### C0055 00

• | The ignition is ON.

• | Ignition voltage is greater than 9.5 volts.

#### C0055 5A

• | The ignition is ON.

• | Ignition voltage is greater than 9.5 volts.

• | The brake pedal is not pressed.

• | A DTC is not set for the other wheel speed circuit on the same axle.

### Conditions for Setting the DTC

#### C0055 00

• | An open is detected on the rear wheel speed sensor signal circuit.

• | A short to ground is detected on the rear wheel speed sensor signal circuit.

• | A short to voltage is detected on the rear wheel speed sensor signal circuit.

#### C0055 5A

The EBCM detects an erratic rear wheel speed signal.

### Action Taken When the DTC Sets

• | The EBCM disables the Antilock Brake System (ABS)/Traction Control System (TCS) for the duration of the ignition cycle.

• | The electronic brake distribution (EBD) does not function optimally.

• | The ABS indicator turns ON.

### 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.

### Diagnostic Aids

If 2 or more wheel speed sensors are inoperative diagnose each wheel speed sensor individually.

An ECE 13 response may be required, after repairs are made, and DTCs are cleared, operate the vehicle at speeds greater than 13 km/h (8 mph) to complete the self test, and the EBCM will turn off the ABS indicator.

#### C0055 5A, 00

If the customer comments that the ABS indicator is ON only during moist environmental conditions: rain, snow, vehicle wash, etc., inspect the wheel speed sensor wiring for signs of water intrusion. Also, a condition may result in a stored history DTC C0055 , this DTC can set if a customer turns the ignition key from the RUN position to the ACCESSORY and leaves it for more than 1 second. The DTC may be stored in history due to a software condition in the EBCM, and no repairs are necessary. If the ABS indicator illuminates intermittently , clear all DTCs and simulate the effects of water intrusion by using the following procedure:

1. Spray the suspected area with a 5 percent saltwater solution. To create a 5 percent saltwater solution, add 2 teaspoons of salt to 8 fl oz of water (10 g of salt to 200 ml of water).
2. Test drive the vehicle over various road surfaces: bumps, turns, etc., above 40 km/h (25 mph) for at least 30 seconds.
3. Rinse the area thoroughly when completed.

### Reference Information

#### Schematic Reference

Antilock Brake System Schematics

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Testing

1. Use a scan tool in order to clear the DTCs. Cycle the ignition to OFF and then start the engine. A current failure will set a DTC.

⇒ | If the DTC does not reset, go to Diagnostic Aids.

2. Turn OFF the ignition and disconnect the EBCM harness connector. At the EBCM harness connector terminal 28, test for 10 volts on the vehicle speed signal circuit.

⇒ | If the voltage is below 10 volts, test for an open or short to ground on the vehicle speed signal circuit. If all circuits test normal, replace the EBCM.

3. Ignition ON, verify that a test lamp does not illuminates between the vehicle speed signal circuit terminal 28 and ground.

⇒ | If the test lamp illuminate, test the vehicle speed signal circuit for a short to B+. If the circuit tests normal, replace the EBCM.

4. If all circuits test normal, replace the PCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM/BPMV or PCM replacement, setup, and programming