Antilock Brake System
DTC C0055 or P0609
DTC Descriptors
DTC C0055 00
Rear Wheel Speed Sensor Circuit
DTC C0055 5A
Rear Wheel Speed Sensor Circuit Erratic Signal
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
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.
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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for a voltage signal from the PCM.
4. This step tests for a missing or erratic vehicle speed signal from the PCM. An assistant may be required to perform this test.
