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. If the PSCM does not receive the vehicle speed message, it sets DTC C0000.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0000 Vehicle Speed Information Circuit

Conditions for Running the DTC

    • The ignition is ON.
    • DTC U1300 or U1301 are not set.

Conditions for Setting the DTC

The PSCM receives an invalid, or no vehicle speed message from the engine control module (ECM).

Action Taken When the DTC Sets

    • DTC C0000 is stored in memory.
    • The instrument panel cluster (IPC) displays the SERVICE VEHICLE SOON warning indicator.
    • Steering assist is set to a default level.

Conditions for Clearing the DTC

    • A current DTC will clear on the next malfunction-free ignition cycle.
    • A history DTC will clear after 100 consecutive malfunction-free ignition cycles.

Test Description

The numbers below refer to the step numbers 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

Schematic Reference: Power Steering Schematics

Connector End View Reference: Power Steering Connector End Views

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. Select Transmission Diagnostic Trouble Codes (DTC) with the scan tool.

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. Clear the electric power steering (EPS) DTCs with the scan tool.
  2. Operate the vehicle within the Conditions for Running the DTC.

Does DTC C0000 reset?

Go to Step 2

System OK