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:  Transmission Control Module (TCM) Read Only Memory (ROM)

DTC P0602:  Transmission Control Module (TCM) Not Programmed

DTC P0603:  Transmission Control Module (TCM) Long Term Memory Reset

DTC P0604:  Transmission Control Module (TCM) Random Access Memory (RAM)

DTC P062F:  Transmission Control Module (TCM) Long Term Memory Performance

Circuit/System Description

This is an internal fault detection of the control solenoid (w/body and TCM) valve assembly. This fault is handled inside the control solenoid (w/body and TCM) valve assembly and no external circuits are involved.

Conditions for Running the DTC

    • The control solenoid (w/body and TCM) valve assembly runs the program to detect an internal fault when the key is ON or the engine is running.
    • Ignition voltage is 8-18 volts.

Conditions for Setting the DTC

The control solenoid (w/body and TCM) valve assembly has detected an internal malfunction.

Action Taken When the DTC Sets

    • DTCs P0601, P0602, P0603, P0604, and P062F are Type A DTCs.
    • The TCM shifts to a default gear, shuts down, and turns OFF.

Conditions for Clearing the DTC

DTCs P0601, P0602, P0603, P0604, and P062F are Type A DTCs.

Diagnostic Aids

When attempting to set TCM internal DTCs let the engine run for at least 1 minute and then shut the engine off for 30 seconds. Following this procedure will allow for a complete TCM shutdown. Reprogram the TCM and retest the DTC to see if the DTC resets.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

DTC Type Reference

    •  Diagnostic Trouble Code (DTC) Type Definitions
    •  Diagnostic Trouble Code (DTC) List/Type

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Circuit/System Verification

  1. Start the engine.
  2. Let the engine run for 1 minute, then shut the engine OFF for 30 seconds.
  3. Retest for DTCs P0601, P0602, P0603, P0604, and P062F.

Circuit/System Testing

Reprogram the TCM and recheck for DTCs.

If the DTC resets, replace the control solenoid (w/body and TCM) valve assembly.

Component Testing

Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Perform the Service Fast Learn Adapts