2ML70 - Automatic Transmission
DTC P0634
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.
DTC Descriptor
DTC P0634
- Transmission Control Module (TCM) Overtemperature
Diagnostic Fault Information
Circuit/System Description
The transmission control module has a built-in temperature sensor to detect possible over-temperature conditions of the transmission control module. This fault indicates the transmission control module is in an overtemperature condition and the transmission control module has shut down to protect from possible heat damage. The transmission control module will remain off until the over temperature condition no longer exists. The transmission control module is part of the control solenoid valve assembly and is not serviced separately.
Conditions for Running the DTC
* The ignition voltage is 11-18 V.
* The transmission control module temperature is -50°C (-58°F) to 146°C (295°F) for 5 seconds.
Conditions for Setting the DTC
* The transmission control module has detected an internal overtemperature condition greater than 141°C (286°F) for 2 seconds.
* The ignition voltage is greater than 18 V and the transmission control module temperature is greater than 50°C (122°F).
Action Taken When the DTC Sets
* DTC P0634 is a Type A DTC.
* The TCM shifts to a default gear 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 the control solenoid valve assembly inspection procedure before replacing the control solenoid valve assembly.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics 2ML70 - Automatic Transmission
Connector End View Reference
Component Connector End Views Connector End Views By Name
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Circuit/System Verification
1. Verify that DTC P0563 is not set.
• If DTC is set, refer to DTC P0562 or P0563 2ML70 - Automatic Transmission.
2. Ignition ON, observe the scan tool Trans. Fluid Temp. parameter. The reading should be less than 141°C (286°F).
• If greater than the specified range, test for a transmission overheat condition.
3. Observe the scan tool TCM temperature parameter. The reading should be less than 141°C (286°F).
• If greater than the specified range, replace the Q8 control solenoid assembly.
Component Testing
* Transmission Fluid Level and Condition Check Transmission Fluid Level and Condition Checkprocedure.
* Line Pressure Check Line Pressure Checkprocedure.
* 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 Verification Tests after completing the diagnostic procedure.
Control Module References Programming and Relearningfor Control Solenoid Valve Assembly replacement, programming and setup.