Kia Optima: Automatic Transaxle Control System / Transaxle Control Module (TCM)

Kia Optima DL3 2019-2021 Service and Repair Manual / Automatic Transaxle System / Automatic Transaxle Control System / Transaxle Control Module (TCM)

Description and operation

The module receives and processes signals from various sensors and implements a wide range of transaxle controls to ensure optimal driving conditions for the driver.


Monitors the vehicle's operating conditions to determine the optimal gear setting.

Performs a gear change if the current gear setting differs from the identified optimal gear setting.

Determines the need for torque converter clutch activation and engages the clutch accordingly.

Calculates the optimal line pressure level by constantly monitoring the torque level and adjusts the pressure accordingly.

Diagnoses the faults and failures for automatic transaxle.


Repair procedures

The automatic transaxle system can be more quickly diagnosed for troubles by using the vehicle diagnostic system (KDS).

KDS provides the following information.


Self diagnosis : Inspects and displays diagnostic trouble code (DTC)


Sensor data : Checks the system input/output value status


Forced operation : Checks the system operating status


Additional function : Controls system options, zero point adjustment and other functions

Component inspection

TCM ground circuit test : Measure the resistance between TCM and chassis ground. (Inspect the terminal connected to the chassis ground with the back of harness connector as the inspection point of TCM side.)

Specification : Below 1Ω


TCM connector test : Disconnect the TCM connector and visually check the ground terminals on TCM side and harness side for bent pins or poor contact pressure.


If problem is not found in Steps 1 and 2, the TCM could be faulty.

If so, replace the TCM with a new one, and then check the vehicle again. If the vehicle operates normally then the problem was likely with the TCM.


Reinspection of original TCM : Install the original TCM (probably broken) into a known-good vehicle and check the vehicle. If the problem occurs again, replace the original TCM with a new one.

If the problem does not reoccur, this is an intermittent problem and other part may be faulty.


Remove the TCM.

(Refer to Engine Control / Fuel System - "Engine Control Module")


Install the TCM.

(Refer to Engine Control / Fuel System - "Engine Control Module")

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