The control solenoid (w/body and TCM) valve assembly has a built-in TCM temperature sensor to detect possible overtemperature conditions of the TCM. This fault indicates the TCM is in an overtemperature condition and the TCM has shut down to protect itself from possible heat damage. The TCM will remain off until the over temperature condition no longer exists.

Fail Case 1

The TCM has detected an internal overtemperature condition greater than 144°C (291°F) for 5 seconds or greater.

Fail Case 2

Ignition voltage is 18 volts or greater 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. Inspect for any obstructions in the cooling system airflow which may cause an overheat condition. 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 for control solenoid (w/body and TCM) valve assembly information.

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Start the engine and check for DTC P0634.

1. Ignition ON, review the Failure Records when the DTC set. Verify the scan tool ECT Sensor parameter was less than 125°C (257°F).

⇒	If greater than the specified range, refer to Engine Overheating .

2. Perform the Transmission Fluid Check to verify correct fluid level and condition. The transmission fluid level should be within the crosshatch band and the transmission fluid should be red or dark brown.

⇒	If the transmission fluid is low or discolored, refer to Transmission Fluid Replacement .

3. Operate the vehicle within the conditions for running and setting the DTC. Verify the scan tool TCM Temperature parameter is less than 146°C (295°F).

⇒	If greater than the specified range, inspect the transmission cooling system for the items list below and repair as necessary. If all the items test normal, replace the control solenoid (w/body and TCM) valve assembly:

•	Obstructions to the airflow of the radiator or transmission due to debris

•	Kinked of damaged transmission fluid lines

•	Damage to the transmission cooler

4. Perform the Transmission Fluid Cooler Flushing and Flow Test to verify proper transmission oil cooler flow.
5. If all the items test normal, test or replace the control solenoid (w/body and TCM) valve assembly.
6. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.