6T70/6T75 - 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 Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC P0634
- Control Module Overtemperature

Circuit/System Description

The transmission control module (TCM) temperature sensor is located inside of the control solenoid valve assembly which has no serviceable components. The TCM monitors the TCM sensor for over temperature protection.

Conditions for Running the DTC

* The ignition voltage is 8.6 volts or greater.
* The TCM temperature is between 0-170°C (32-338°F) for 0.25 second or greater.
* DTC P0634 is not set.

Conditions for Setting the DTC

Condition 1

The TCM detects an internal temperature condition of 146°C (295°F) or greater for 5 seconds.

Condition 2

The ignition voltage is 18 volts or greater and the TCM detects an internal temperature condition of 50°C (122°F) or greater for 2 seconds.

Action Taken When the DTC Sets

* DTC P0634 is a Type A DTC.
* The TCM limits the transmission to Reverse and 5th gear operation.
* The TCM inhibits Tap Up/Down function.
* The TCM inhibits manual shifting of forward gears.
* The TCM commands maximum line pressure.
* The TCM shuts down.

Conditions for Clearing the DTC

DTC P0634 is a Type A DTC.

Reference Information
Description and Operation

Electronic Component Description Electronic Component Description for control solenoid valve assembly
DTC Type Reference

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

Control Module References Control Module References for scan tool information

Circuit/System Verification

Note: If DTC P0218 is set, diagnose that DTC first.

1. Ignition ON, review the Failure Records when the DTC set. Verify the scan tool Engine Coolant Temperature parameter is less than 125°C (257°F).

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

2. Engine running, accessories OFF, measure and record the battery voltage at the battery terminals with a DMM. The voltage should be between 12.6-15.0 volts.

• If not within the specified range, or the charge indicator light is ON, refer to Charging System Test Component Tests and General Diagnostics.

3. Perform the Transmission Fluid Level and Condition Check 6T70/6T75 - Automatic Transmission to verify correct fluid level and condition.
4. Perform the Transmission Fluid Cooler Flushing and Flow Test Transmission Fluid Cooler Flushing and Flow Test to verify proper transmission oil cooler flow.
5. Operate the vehicle within the conditions for running and setting the DTC until normal engine temperature is reached. 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 obstructions to the airflow of the radiator or transmission due to debris, kinked, or damaged transmission fluid lines, or damage to the transmission cooler. If all the items test normal, replace the Q8 control solenoid valve assembly.

6. After performing the above steps, verify that the DTC does not reset by operating the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. If the vehicle passes the Circuit/System Verification procedure, refer to Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections.

Repair Instructions

Note:
* Perform the Reset Transmission Adapts 6T70/6T75 - Automatic Transmission following all transmission related repairs.
* Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection Control Solenoid Valve and Transmission Control Module Assembly Inspection.

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

Control Module References Control Module References for control solenoid valve assembly replacement, setup, and programming