GM Service Manual Online
For 1990-2009 cars only

DTC C0055 or P0609 Less than 8600lb GVW

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 00: Rear Wheel Speed Sensor Circuit

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

DTC P0609: Vehicle Speed Output Circuit

Circuit/System Description

The output speed sensor OSS is a hall-effect type sensor. The OSS mounts to the transmission control valve upper body assembly, and connects to the Transmission control module (TCM). As the output shaft rotates, the sensor produces a signal frequency based on the machined surface of the output shaft. this signal is transmitted through the OSS signal circuit to the TCM and on to the ECM. 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 DIC 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.

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 Testing

  1. Ignition OFF disconnect the harness connector at the EBCM.
  2. Ignition ON, test for 9.8 - 10.2 volts between the signal circuit terminal 31 and ground.
  3. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If all circuits test normal, replace the ECM.
    If greater than the specified range, test the signal circuit for a short to voltage. If all circuits test normal, replace the ECM.
  4. If all circuits test normal, replace the EBCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM or ECM replacement, setup, and programming

DTC C0055 or P0609 Equal to or greater than 8600lb GVW

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 01: Rear Wheel Speed Sensor Circuit Short to Battery

DTC C0055 04: Rear Wheel Speed Sensor Circuit Open Circuit

DTC C0055 26: Rear Wheel Speed Sensor Circuit Frequency Too Low

DTC P06090: Vehicle Speed Output Circuit

Circuit/System Description

The output speed sensor OSS is a hall-effect type sensor. The OSS mounts to the transmission control valve upper body assembly, and connects to the Transmission control module (TCM). As the output shaft rotates, the sensor produces a signal frequency based on the machined surface of the output shaft. this signal is transmitted through the OSS signal circuit to the TCM and on to the ECM. 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

The EBCM detects a short to voltage, short to ground or an open/high resistance on the rear wheel speed sensor signal circuit.

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 DIC 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.

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 Testing

  1. Ignition OFF disconnect the harness connector at the EBCM.
  2. Ignition ON, test for 9.8 - 10.2 volts between the signal circuit terminal 20 and ground.
  3. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If all circuits test normal, replace the ECM.
    If greater than the specified range, test the signal circuit for a short to voltage. If all circuits test normal, replace the ECM.
  4. If all circuits test normal, replace the EBCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM or ECM replacement, setup, and programming