Code U0101 – Lost Communication with TCM

If you can’t perform gear changes in the vehicle, it is possible that the computer has stored the U0101 Code, which means that the TCM signal is damaged, if you want to know the causes and solutions, read on.

Description of DTC code U0101

The Automotive TCM is a system implemented in vehicles with automatic transmission, it is in charge of coordinating gear changes, that is to say, it works together with the ECM thanks to the Control Area Network (CAN).

The ECM sends signals to the TCM to perform the gear changes needed by the car, so it adjusts to the driving conditions, therefore, when the ECM does not receive the signal or cannot perform a communication exchange with the TCM, then it stores the U0101 Code.

Symptoms of fault code U0101

  • Check engine light comes on
  • Cannot shift gears or speeds
  • As a safety mode, the vehicle is stuck in 2nd or 3rd gear.

Causes of OBD2 code U0101

For DTC U0101 to be stored, it is possible that it is as a result of the following:

  • The Control Area Network is faulty.
  • The CAN-BUS is open
  • The TCM circuit is faulty

Possible Solutions for DTC U0101

  • When Code U0101 is stored it is possible that other DTCs are stored, therefore we recommend you check for CAN-BUS faults or Battery faults.
  • Check the TCM fuses, if they are shorted or not properly fastened proceed to repair.
  • Check the CAN-BUS wiring, inspect that all connections are in perfect condition, in case of finding damaged cables repair them.
  • If everything is correct and you think that the TCM has faults, we recommend you to take it to a specialized workshop.

Liam Dare

As CEO of, my passion for the automotive world motivates me to build online businesses that provide information and entertainment to users. I am proud to contribute in a positive way to the automotive community.