GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 Terrain 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0601, P0602, P0603, P0604, P0605, P0606, P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610

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 P0604: Control Module Random Access Memory (RAM)

DTC P0606: 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 or P0604

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

P0602

    • The ignition is ON or the engine is running.
    • The DTC runs continuously once the above conditions are met.

P0606

    • The engine speed is greater than 1,200 RPM.
    • The ignition voltage is greater than 7 volts.
    • The DTC runs continuously once the above conditions are met.

Conditions for Setting the DTC

P0601

The ECM detects the incorrect read only memory (ROM) checksum for greater than 30 seconds.

P0602

The ECM detects that programming is incomplete for greater than 1 second.

P0604

The ECM detects random access memory (RAM) errors for greater than 5 seconds.

P0606

The ECM detects an internal condition for greater than 5 seconds.

Action Taken When the DTC Sets

DTCs P0601, P0602, P0604, and P0606 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P0601, P0602, P0604, and P0606 are Type A DTCs.

Reference Information

Description and Operation

Engine Control Module Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Circuit/System Verification

Ignition ON, observe the DTC information with a scan tool. DTCs P0601, P0602, P0604, and P0606 should not set.

⇒If DTCs P0601 or P0604 failed this ignition, replace the ECM.
⇒If DTC P0606 is set with P0638 or P2119 refer to Diagnostic Trouble Code (DTC) List - Vehicle .

Circuit/System Testing

P0602

Program the ECM. If DTC P0602 sets after programming, perform the following steps:

    • Ensure that all tool connections are secure.
    • Ensure the programming equipment is operating correctly.
    • Ensure the correct software and the correct calibration is used.
    • Attempt to program the ECM.
       ⇒If DTC P0602 sets, replace the ECM.

P0606

  1. Observe the Freeze Frame/Failure Records with a scan tool.
  2. Clear the DTCs with a scan tool.
  3. Ignition OFF for 30 seconds.
  4. 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.
    5. ⇒If DTC P0606 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