GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 Chevy Suburban - 2WD 🢒 DTC 🢒 DTC C056D

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 provide an overview of each diagnostic category.

DTC Descriptor

DTC C056D 39: ECU Hardware Performance Internal Electronic Failure

Circuit/System Description

The power steering control module (PSCM) continuously monitors the internal circuitry within the module.

Conditions for Running the DTC

Ignition ON.

Conditions for Setting the DTC

This DTC will set if the PSCM detects an internal malfunction within the module.

Actions Taken When DTC Sets
    • DTC C056D is stored in memory.
    • The driver information center (DIC) displays the SERVICE POWER STEERING warning message.
    • No steering assist.

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, without the repeat of the internal malfunction.

Reference Information

Schematic Reference

Power Steering Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Steering System 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 Verification

Danger: Always perform the High Voltage Disabling procedure prior to servicing any High Voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.

The High Voltage Disabling procedure will perform the following tasks:

   • Identify how to disable high voltage.
   • Identify how to test for the presence of high voltage.
   • Identify condition under which high voltage is always present and personal protection equipment (PPE) and proper procedures must be followed.
Failure to follow the procedures exactly as written may result in serious injury or death.

Important: Verify the motor connector is securely connected and not loose.

  1. Verify that DTC C056D is not set.
    2. ⇒If the DTC is set, replace the PSCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for PSCM replacement, setup, and programming