Antilock Brake System - Non-Hybrid Greater than/Equal to 3900 kg (8600 lb) GVW
DTC C0055 or P0609
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.
DTC Descriptors
DTC C0055 01
- Rear Wheel Speed Sensor Circuit Short to Battery
DTC C0055 04
- Rear Wheel Speed Sensor Circuit Open
DTC C0055 08
- Rear Wheel Speed Sensor Circuit Signal Invalid
DTC C0055 0F
- Rear Wheel Speed Sensor Circuit Erratic
DTC C0055 26
- Rear Wheel Speed Sensor Circuit Frequency Too Low
DTC P0609
- Vehicle Speed Output Circuit
Diagnostic Fault Information
Circuit/System Description
The vehicle speed sensor, also called the output shaft speed sensor creates an AC voltage as the rotor teeth pass through the magnetic field of the sensor. The transmission control module (TCM) converts the AC voltage into a vehicle speed signal, which is used to determine shift timing and torque converter clutch scheduling. The TCM also provides a replicated transmission output speed signal to the engine control module (ECM).
The ECM converts the data from the output speed signal to a 128K pulses/mile engine speed signal. The electronic brake control module (EBCM) uses the signal from the ECM in order to calculate the rear wheel speed.
Conditions for Running the DTC
* Ignition ON.
* Ignition voltage is greater than 10 volts.
Conditions for Setting the DTC
* The EBCM detects a short to voltage, short to ground or an open/high resistance on the rear wheel speed sensor signal circuit.
* The replicated output speed signal is erratic or has electrical noise on the signal causing the 128K pulses/mile engine speed signal to lose pulses.
* A defective transmission vehicle speed sensor or output speed sensor can cause inaccurate speed reading, creating faulty replicated output speed signal.
Action Taken When the DTC Sets
* The EBCM disables the Antilock Brake System (ABS) 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
* Visually inspect the vehicle speed sensor or output speed sensor for cracks or damage.
* Ensure the vehicle speed sensor or output speed sensor is properly torqued.
* Inspect the internal tone ring or gear teeth for damage.
* Check for missing pulses or electrical noise on the replicated transmission output speed signal.
Reference Information
Schematic Reference
Antilock Brake System Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
ABS Description and Operation (Without JL4) (ABS (Without JL4))ABS Description and Operation (With JL4) (ABS (With JL4))
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 (Control Module References)for scan tool information
Circuit/System Verification
Note: A condition may result in a stored history DTC C0055, check the replicated transmission output speed signal circuit for damaged wires, missing pulses or electrical noise that may be passed to 128K pulses/mile engine speed signal.
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, check the replicated transmission output speed signal circuit for damaged wires, missing pulses or electrical noise that may be passed to 128K pulses/mile engine speed signal.
1. Ignition OFF, disconnect the harness connector at the EBCM.
2. Ignition ON, test for greater than 10 V between the signal circuit terminal 20 and ground.
• If less than 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 appropriate harness connector listed below at the ECM:
* X1 (LY6)
* X2 (LGH or LML)
4. Ignition ON, verify that a test lamp does not illuminate between the appropriate signal circuit terminal listed below and ground.
* Terminal 57 X1 (LY6)
* Terminal 27 X2 (LGH or LML)
• 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 (Verification Tests) after completing the diagnostic procedure.
Control Module References (Control Module References)for EBCM or ECM replacement, programming and setup