Vehicles Less Than 8600LB GVW

DTC C0055 or P0609 (Less than 8600lb GVW)

Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Diagnostic System Check - Vehicle
• Review Strategy Based Diagnosis for an overview of the diagnostic approach. Strategy Based Diagnosis
• Diagnostic Procedure Instructions provides an overview of each diagnostic category. Diagnostic Procedure Instructions

DTC Descriptors
DTC C0055 00: Rear Wheel Speed Sensor Circuit
DTC C0055 5A: Rear Wheel Speed Sensor Circuit Erratic Signal
DTC P0609: Vehicle Speed Output Circuit

Diagnostic Fault Information

Circuit
Rear Wheel Speed Sensor Signal
Short to Ground C0055 00
Open/High Resistance C0055 00
Short to Voltage C0055 00
Signal Performance C0055 5A

Circuit/System Description
The vehicle speed sensor (VSS) also called the output speed sensor (OSS) creates a AC voltage signal that increases in frequency as vehicle speed increases. The transmission control module (TCM) receives and process this signal. The TCM provides a digital VSS signal on the data communication line to the engine control module (ECM) and other controllers connected to the data line. 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
• The ignition is ON.
• Ignition voltage is greater than 10 volts.

Conditions for Setting the DTC
C0055 00 or P0609
The EBCM detects a short to voltage, short to ground or an open/high resistance 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.
• A driver information center message and/or a warning indicator may be displayed.

Conditions for Clearing the DTC
• The condition for setting the DTC is no longer present.
• The EBCM 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 Diagrams

Connector End View Reference
Antilock Brake System Connector End Views Connector Views

Description and Operation
ABS Description and Operation Description and Operation

Electrical Information Reference
• Circuit Testing Circuit Testing
• Connector Repairs Connector Repairs
• Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs Wiring Repairs

Scan Tool Reference
Control Module References for scan tool information

Circuit/System Verification

Note: 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.

1. Verify that no DTCs are set in the ECM or TCM.
--> If DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. Diagnostic Trouble Code (DTC) List - Vehicle

2. Observe the scan tool Rear Wheel Speed parameter. The rear wheel speed reading should be within 2 mph of the front speed sensors when driving in a straight line at a speed greater than 20 km/h (13 mph).
--> If not within the specified range, refer to Circuit/System Testing.

3. Operate the vehicle within the Conditions for Running the DTC, to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

Note: 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.

1. Ignition OFF disconnect the harness connector at the EBCM.

2. Ignition ON, test for greater than 10 Volts between the signal circuit terminal 31 and ground.
--> If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition OFF, disconnect the X1 harness connector at the ECM.

4. Ignition ON, verify that a test lamp does not illuminate between the appropriate signal circuit terminal listed below and ground.
• Terminal 50 X1 (4.3L)
• Terminal 57 X1 (4.8L, 5.3L, 6.0 and 6.2L)
--> If the test lamp illuminates, test the signal circuit for a short to voltage.

5. If the circuit tests normal, replace the EBCM.

Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
Control Module References for EBCM or ECM replacement, setup, and programming Control Module References