Transmission Control Module (TCM)
Name: Transmission control unit
Location: Typically found under the hood of the vehicle, attached to the side of the transmission.
Functions:
* Controls automatic transmission gear shifting.
* Monitors and regulates transmission fluid pressure.
* Monitors engine and vehicle parameters to optimize gear shifts.
* Communicates with other vehicle electronic modules such as the ECM (Engine Control Module).
Possible signs of malfunction:
* Problems with gear shifting (delay, slipping, harsh shifts)
* Engine speed too high or too low
* Increased fuel consumption
* Flashing or illuminated transmission fault light
Diagnostics:
* Read fault codes using diagnostic scanner
* Physical inspection of the control unit and its wiring for damage
*Checking transmission fluid pressure and fluid condition
Replacement:
* If the transmission control unit is faulty, it must be replaced.
* Be sure to use a new or remanufactured part from an authorized Toyota dealer.
*After replacing the transmission control module, reprogramming or calibration may be required.
Original part numbers:
* 89530-28190
* 89530-28240
* 89530-28290
* 89530-3A880
* 89530-3A920
Note: Part numbers may vary depending on vehicle year and model.