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 P0607: Control Module Performance

DTC P1607: Control Module Ignition Off Timer Performance.

DTC P1650: Control Module Internal Performance.

DTC P1655: Control Module Internal Performance.

Circuit/System Description

This diagnostic applies to internal microprocessor integrity conditions within the engine control module (ECM). This diagnostic also addresses if the ECM is not programmed.

Conditions for Running the DTC

P0601

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

P0607

    • The ignition is ON.
    • The ignition voltage is greater than 11 volts.
    • The DTC runs continuous once the above conditions are met.

P1607

    • The ignition is ON.
    • The DTC runs once an ignition cycle.

P1650 and P1655

    • The ignition is ON.
    • 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.

P0607

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

P1607, P1650, and P1655

The ECM detects a low power counter error for greater than 3 seconds.

Action Taken When the DTC Sets

    • DTC P0601 is a Type A DTC.
    • DTC P1655 is a Type B DTC.
    • DTCs P0607, P1607, and P1650 are Type C DTCs.

Conditions for Clearing the DTC

    • DTC P0601 is a Type A DTC.
    • DTC P1655 is a Type B DTC.
    • DTCs P0607, P1607, and P1650 are Type C 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, P0607, P1607, P1650, and P1655 should not set.

If DTCs P0601, P0607, P1607, P1650, or P1655 failed this ignition, replace the ECM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module replacement, setup, and programming