6L50 / 6L80 / 6L90 Automatic Transmission

DTC P0601, P0602, P0603, P0604, or P1621

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 P1621

Transmission Control Module (TCM) Long Term Memory Performance

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

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 P1621 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 P1621 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 P1621.

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. Control Solenoid Valve and Transmission Control Module Assembly Inspection

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Perform the Service Fast Learn Adapts. Programming and Relearning