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 DTC indicates the TCM is in an overtemperature condition and the TCM has shut down to protect it from possible heat damage. This fault is handled inside the TCM and no external circuits are involved. The TCM will remain off until the overtemperature condition no longer exists.

Condition 1

The TCM has detected an internal overtemperature condition greater than 142°C (288°F) for 5 seconds.

Condition 2

Ignition voltage is equal to or greater than 18 volts and the TCM temperature is greater than 50°C (122°F) for 2 seconds.

DTC P0634 is a Type A DTC.

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 the Control Solenoid Valve and Transmission Control Module Assembly Inspection before replacing the control solenoid (w/body and TCM) valve assembly.

Description and Operation

Electronic Component Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Start the engine and check for DTC P0634.

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.

Perform the 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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Control solenoid (w/body and TCM) valve assembly replacement. Refer to Control Module References for replacement, setup, and programming.
2. Perform the Service Fast Learn Adapts if internal transmission repairs are performed.