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

    •  Automatic Transmission Inline 16-Way Connector End View
    •  Automatic Transmission Internal Connector End Views
    •  Automatic Transmission Related 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 .