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 P0602: Control Module Not Programmed

DTC P0603: Control Module Long Term Memory Reset

DTC P0604: Control Module Random Access Memory (RAM)

DTC P0606: Control Module Internal Performance

DTC P167D: Control Module Ignition Coil Internal Circuit

DTC P2610: Control Module Ignition Off Timer 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 checksum calculation at power down in the last drive cycle was completely finished. DTC P0601 runs once an ignition cycle when the condition is met for 30 seconds at ignition OFF.

P0602

The ignition is ON, with the engine OFF. DTC P0602 runs continuously when the ignition is ON for greater than 1 second.

P0603

    • The ignition is ON.
    • The power down calculation in the last drive cycle was completely finished.
    • DTC P0603 runs continuously when the conditions above have been met for greater than 5 seconds.

P0604

The read/write test at power down in the last drive cycle completely finished. DTC P0604 runs once an ignition cycle when the condition is met for greater than 5 seconds at ignition OFF.

P0606

The power down calculation in the last drive cycle was completely finished. DTC P0606 runs continuously with the ignition ON or engine operating for greater than 5 seconds.

P167D

    • The engine is operating.
    • The igniting voltage is between 9-18 volts.
    • The engine speed is less than 6000 RPM.
    • DTC P167D runs continuously when the conditions above are met.

P2610

    • The engine speed is greater than 240 RPM.
    • DTC P2610 runs continuously when the engine is operating and the real time clock is active.

Conditions for Setting the DTC

P0601

The ECM detects a read only memory (ROM) checksum error at ECM power up. The error is detected 5 times, then a 5 second delay for MIL ON after the fifth detection.

P0602

The ECM detects that programming is incomplete. The condition exists, then a 5 second delay for MIL ON.

P0603

The ECM detects a reset error of the internal software that operates the throttle actuator control (TAC) system, during the shut down path test. The condition exists, then a 5 second delay for MIL ON.

P0604

The ECM detects random access memory (RAM) errors. The condition exists, then a 5 second delay for MIL ON.

P0606

The ECM detects an internal error of the monitoring software for the throttle actuator control (TAC) system. The condition exists, then a 5 second delay for MIL ON.

P167D

The ECM detects a condition with the integrated circuits of the ignition driver module for greater than 4 seconds, or for a cumulative time of 30 seconds.

P2610

The ECM detects the engine off timer signal is missing or not valid for greater than 1 second, or a cumulative of 10 seconds.

Action Taken When the DTC Sets

    • DTCs P0601, P0602, P0603, P0604, P0606, and P167D are Type A DTCs.
    • DTCs P167D and P2610 are Type B DTCs.

Conditions for Clearing the DTC

    • DTCs P0601, P0602, P0603, P0604 and P0606 are Type A DTCs.
    • DTCs P167D and P2610 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 Verification

  1. Ignition ON, observe the DTC information with a scan tool. DTC P0602 or P0606 should not set.
  2. If DTC P0602 failed this ignition, program the ECM. If the DTC resets, replace the ECM.
    If DTC P0606 failed this ignition, clear the DTCs with a scan tool and verify the DTC does not reset. If the DTC resets, replace the ECM.
  3. Observe the DTC information with a scan tool. DTC P0601, P0603, P0604, P167D or P2610 should not set.
  4. If a DTC failed this ignition, replace the ECM.
  5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming