P0634

DTC P0634

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 P0634
- Transmission Control Module (TCM) Overtemperature




Circuit/System Description

The control solenoid (w/body and TCM) valve assembly has a built-in TCM temperature sensor to detect overtemperature conditions and is not serviced separately. TCM power will produce heat that is absorbed by the internal heat sink. As long as the heat sink and the controller base plate stay below 142°C (288°F), the TCM will stay operational (no overtemperature shut down). This fault indicates the TCM is in an overtemperature condition and the TCM has shut down to protect it from possible heat damage. The TCM will remain off until the overtemperature condition no longer exists.


Conditions for Running the DTC

* Ignition voltage is between 8.6-18.0 volts.
* The TCM temperature is less than 150°C (302°F) for greater than 5 seconds.
* DTC P0634 is not currently active and has not failed in the current key on.



Conditions for Setting the DTC

The TCM has detected an internal overtemperature condition greater than 141°C (286°F) for 10 seconds.


Action Taken When the DTC Sets

* DTC P0634 is a Type A DTC.
* The TCM shifts to a default gear, shuts down, and turns OFF.



Conditions for Clearing the DTC

DTC P0634 is a Type A DTC.


Diagnostic Aids

Inspect the transmission cooler, transmission fluid lines, engine cooling system, and transmission fluid level, and inspect for any obstructions in the cooling system airflow which may cause an overheat condition. Inquire about customer towing or extreme driving conditions. An engine cooling system or transmission cooling system malfunction may cause this diagnostic to set. Perform theControl Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection) before replacing the control solenoid (w/body and TCM) valve assembly.


Reference Information
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

Start the engine and check for DTC P0634.


Circuit/System Testing

1. Start the engine.
2. Observe the transmission fluid temperature (TFT) and the engine coolant temperature (ECT). Ensure there are no current overheat conditions present in these systems.

• If an overheating concern is found, diagnose and repair that system first.

3. Operate the vehicle under the same conditions as found in Failure Records and observe the TCM Temperature parameter on the scan tool.
4. Recheck for DTCs.

• If the DTC resets, and the TCM power-up temperature sensor is not over 130°C (266°F), and the TFT is less than 120°C (248°F), replace the control solenoid (w/body and TCM) valve assembly.
• If the TCM power-up temperature sensor is over 130°C (266°F), inspect and repair the transmission cooler, transmission cooler fluid lines, engine cooling system, and transmission fluid level, and inspect for any obstructions in the cooling system airflow which may cause an overheat condition.

5. Inquire about customer towing or extreme driving conditions.



Component Testing

Perform theControl Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection) . Look for apparent TCM damage or any conditions that would cause temperature problems, such as severe sediment or debris build up.


Repair Instructions

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

* Control Module References (Programming and Relearning) for control solenoid (w/body and TCM) valve assembly replacement, setup, and programming.
* Perform theService Fast Learn Adapts (Programming and Relearning) if internal transmission repairs are performed.