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 Descriptors

DTC P0601: Control Module Read Only Memory (ROM)

DTC P0604: Control Module Random Access Memory (RAM)

DTC P0605: Control Module Programming Read Only Memory (ROM)

Circuit/System Description

This diagnostic applies to internal microprocessor integrity conditions within the engine control module (ECM).

Conditions for Running the DTC

    • The ignition is ON or the engine is running.
    • The DTCs run once an ignition cycle.

Conditions for Setting the DTC

P0601

The ECM detects that the checksum calculation does not match the expected checksum.

P0604 or P0605

The ECM detects an internal condition for more than 3 seconds.

Action Taken When the DTC Sets

DTCs P0601, P0604, and P0605 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0601, P0604, and P0605 are Type B DTCs.

Reference Information

Description and Operation

Engine Control Module Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Circuit/System Testing

Ignition ON, observe the DTC information with a scan tool. DTCs P0601, P0604, or P0605 should not set.

If DTCs P0601, P0604, or P0605 failed this ignition, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming.