GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The power steering control module (PSCM) receives a vehicle speed message from the powertrain control module (PCM) via the serial data circuit. The PSCM uses this vehicle speed message, and other inputs, to determine the desired amount of steering assist. At lower speeds, more assist is provided for easy turning during parking maneuvers. At higher speeds, less assist is provided for improved road feel and directional stability.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0000 Vehicle Speed Information Circuit

This vehicle has DTCs which include DTC symptoms. For more information on DTC symptoms, refer to DTC Symptom Description .

DTC Symptom

DTC Symptom Descriptor

71

Invalid Serial Data Received

Conditions for Running the DTC

    • The ignition is ON.
    • DTCs U2100, U2105, 2107, or U2109 are not set.
    • Power Steering System voltage is between 6-16 volts.

Conditions for Setting the DTC

The PSCM receives an invalid vehicle speed message from the PCM.

Action Taken When the DTC Sets

    • DTC C0000 71 is stored in memory.
    • The DIC displays the POWER STEERING warning message.
    • Steering assist is set to a default level.
    • Poor return to center

Conditions for Clearing the DTC

    • A current DTC will clear when the malfunction is no longer present.
    • A history DTC will clear after 100 consecutive malfunction-free ignition cycles.
    • Using a scan tool

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests for the presence of vehicle speed related DTCs in the control module where the vehicle speed message originates.

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With the scan tool, select Powertrain Diagnostic Trouble Codes (DTC) function.

Does the scan tool indicate the presence of any vehicle speed related DTCs?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3

  1. Use the scan tool in order to clear the DTC.
  2. Operate the vehicle within the conditions for running the DTC.

Does the DTC reset?

Go to Step 2

System OK