GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 DTC 🢒 DTC C0564

Circuit Description

The electro-hydraulic power steering (EHPS) operates when voltage at the EHPS connector is in the range of 34-50 volts. The EHPS will go into standby mode if the supply voltage at the EHPS connector drops below 18 volts for more than 10 milliseconds. The EHPS module shall be turned back on once the supply voltage rises above 22 volts, without a key cycle being required. If the supply voltage drops below 12 volts, the EHPS module drivers shall shut down and a key cycle will be required to reset. The EHPS module shall withstand voltages up to a transient voltage of 58 volts for 400 milliseconds. If the supply voltage exceeds 55 volts, the EHPS module drives shall shut down and a key cycle will be required to reset. The 36 volts power supply is grounded directly to the negative terminal of the EHPS.

Conditions for Running the DTC
    • EHPS module in RUN mode.
    • Ignition switch in ACC or ON position.
    • Battery voltage between 12-58 volts.

Conditions for Setting the DTC
    • The EHPS module cannot validate the checksum from a programming event (software checksum error).
    • A replacement EHPS powerpack has been installed and not programmed.

Action Taken When the DTC Sets
    • The SERVICE BRAKE SYSTEM message and SERVICE STEER SYSTEM message will be displayed.
    • A chime will sound.
    • EHPS module operation is reduced and the electric motor control is inactive.
    • Stores DTC C0564 in the powertrain control module (PCM).
    • History DTC C0564 will be set in PCM.

Conditions for Clearing the DTC
    • After a successful programming event.
    • Using the scan tool.
    • A history DTC will clear after 255 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids
    • It may be necessary to perform the programming procedure more than once.
    • It may be necessary to check Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. This step checks to see if the problem has cleared after the EHPS control module has been reprogrammed.

Step

Action

Yes

No

Schematic Reference: Power Steering Schematics

Connector End Views Reference: Power Steering Connector End Views

1

Did you perform the electro-hydraulic power steering (EHPS) Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Power Steering System

2

  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. Use the scan tool to clear the DTC.
  4. Reprogram the EHPS control module. Refer to Service Programming System (SPS) in Programming.
  5. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 3

System OK

3

Important: Always perform the calibration procedure for the brake pedal position (BPP) sensor. Refer to Brake Pedal Position Sensor Calibration Description and Operation .

Replace the EHPS powerpack. Refer to Power Steering Pump Replacement .

Did you complete the replacement?

Go to Step 4

--

4
  1. Use the scan tool to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK