GM Service Manual Online
For 1990-2009 cars only

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 Descriptor

DTC P1640 00: Control Module Power Circuit Malfunction

Circuit/System Description

These DTC apply to internal microprocessor integrity conditions within the engine control module (ECM).

Conditions for Running the DTC

    • The ignition is ON.
    • The DTCs run continuously once the above condition is met.

Conditions for Setting the DTC

The ECM detects an internal EEPROM failure.

Action Taken When the DTC Sets

DTC P1640 is a Type A DTCs.

Conditions for Clearing the DTC

DTC P1640 is a Type A DTCs.

Reference Information

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Circuit/System Testing

  1. Observe the Freeze Frame/Failure Records with a scan tool.
  2. Clear the DTCs with a scan tool.
  3. Ignition OFF for 30 s.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
  5. If DTC P1640 failed this ignition, replace the K20 Engine Control Module (ECM).

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming