Allison - Automatic Transmission

DTC P0602

Diagnostic Instructions

* Perform theDiagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptor
DTC P0602
- Transmission Control Module (TCM) Not Programmed




Circuit/System Description

The transmission control module (TCM) determines if it has a proper calibration. The TCM detects the presence of improper calibration by checksum and name comparison. This is internal to the TCM. No external circuits are involved.


Conditions for Running the DTC

The TCM conducts the test one time at power up.


Conditions for Setting the DTC

The DTC will set if the default calibration is detected.


Action Taken When the DTC Sets

The transmission will go to a hydraulic default shift mode of reverse, neutral and third range.


Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Verification

Ignition on, verify that DTC P0602 does not set.


Circuit/System Testing

1. Recalibrate the TCM. Refer to Control Module References (Programming and Relearning) for TCM replacement, setup, and programming.
2. Ignition on, verify that DTC P0602 does not set.

• If DTC resets, replace the TCM. Refer to Control Module References (Programming and Relearning) for TCM replacement, setup, and programming.

3. Perform fast learn procedure. Refer to FastLearn Procedure (Programming and Relearning) .



Repair Instructions

Perform theDiagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Control Module References (Programming and Relearning) for TCM replacement, setup, and programming.
* FastLearn Procedure (Programming and Relearning)



Repair Verification

If another DTC is present, refer toDiagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) and perform the appropriate diagnostic procedure.