GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Savana 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0601-P0604 or P062F

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 provide 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

The internal fault detection is handled inside the TCM; no external circuits are involved.

Conditions for Running the DTC

This diagnostic applies to internal microprocessor integrity conditions within the TCM. This diagnostic also addresses if the TCM is not programmed.

Conditions for Setting the DTC

The TCM detects an internal condition.

Action Taken When the DTC Sets

P0601, P0603, P0604, and P062F

    • DTC P0601, P0602, P0603, P0604 and P062F are type A DTCs.
    • The TCM commands maximum line pressure.
    • The TCM forces the torque converter clutch (TCC) OFF.
    • The TCM inhibits TCC engagement.
    • The TCM freezes transmission adaptive functions.
    • The TCM commands a soft landing to 2nd gear.

P0602

    • DTC P0601, P0602, P0603, P0604 and P062F are type A DTCs.
    • The TCM commands maximum line pressure.
    • The TCM forces the torque converter clutch (TCC) OFF.
    • The TCM inhibits TCC engagement.
    • The TCM freezes transmission adaptive functions.
    • The TCM commands an immediate landing to 2nd gear.

Conditions for Clearing the DTC

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

Diagnostic Aids

DTC P0602 indicates the TCM is not programmed.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transmission General Description

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Ignition ON, clear the DTC information with a scan tool. Observe the scan tool DTC information. Verify that DTC P0602 does not fail this ignition.
    2. ⇒If DTC P0602 failed this ignition, reprogram the TCM. If DTC P0602 resets, replace the TCM.
  2. Observe the DTC information with a scan tool. Verify that DTC P0601, P0603, P0604, or P062F do not set this ignition cycle.
    3. ⇒If DTC P0601, P0603, P0604, or P062F are set this ignition cycle, replace the TCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for TCM replacement, setup, and programming.