Code U0101 Lost Communication With TCM – [Solved]

Code U0101 Lost Communication With TCM is a trouble code that inform drive that there is a communication problem between vehicle powertrain control module PCM and Transimission control module TCM. PCM get information from TCM through control area network CAN. So if PCM does not recevie TCM signal from CAN then it vehicle show code U0101.

In some vehicles like Ford, Nissan, and Mazda, the trouble code U0101 appears when you scan the vehicle using onboard disgnoistic OBD-II. In very simple words this trouble code U0101 means that the vehicle transmission control module TCM is facing difficulty communicating with rest of car.

As all new models of each and every brand have more of electrical connections that mechanical setup. To make that electrical setup work, vehicles entirely depends on their on their computer setup to integrade and control different electrical components.

So what happen when this integration does not work properly. This is when code U0101 appear and inform its driver that there is a communication error in vehicle electrical setup.

What is Trouble Error Code U0101

Code U0101 appear when there is communication error between transmission control module TCM and rest of the vehicle. TCM give and recevie signal through control area netwok CAN.

The vehicle powertrain control module PCM (system that manage vehicle engine, transmission, and other systems) continuously monitor the vehicle CAN system for signals send my TCM. So when PCM does not receive signal from TCM throug CAN it shows Code U0101.

Does Code U0101 Mean Lost Communication With TCM?

Yes, the code, U0101 means lost communication with TCM. There is a central point of all control modules in the engine. That is called the Controller Area Network bus or CAN bus. The main task of that circuit is to maintain communication between control modules.

But when CAN Bus fails to work, the communication process break then the trouble code U0101 appears on our scanner. So, we can say that code U0101 means lost communication with TCM.

Symptoms Of Diagnostic Trouble Code U0101

Scaner will show trouble code U0101 when you scan your vehicle. There are many possible symptoms of a diagnostic trouble code U0101 that show communication problem with your vehicle computer. It is important to have your vehicle inspected by a professional if you experience any of these. 

The most common symptom will be related to tramission control means transmission shifting will be hard. Some more symptoms are there that are also important to know and they are follow

  • Check Engine Light On
  • Gear Shifting Problem
  • Vehicle Will not Shift to 2nd or 3rd gear from 1st gear
  • Instrument cluster PRNDL display  

If you notice any of these issues, be sure to bring your car in for an inspection as soon as possible so that the problem can be diagnosed and corrected. Also, you need to know the causes of happening this problem to avoid further problems.

Why This Code May Appear?

If the CAN bus fails to maintain communication between the powertrain control module and trasmission control module, this code may appear. So, you need to work on that area if you are planning to fix this code.

Some other possible reasons are

  • faulty battery with voltage issues
  • damaged terminals
  • disconnected connectors
  • damage to the ground connection
  • CAN bus circuit issue
  • Faulty PCM or TCM Control Module

How To Fix Code U0101 Lost Communication With TCM?

There are some checkups only that you can perform to solve trouble code U0101. If those does not work then you have to consult a mechanic as its not possible to repair or diagnose code U0101 thourgh DIY.

Checkup starts with the battery as dead battery or battery with low voltage will make it difficult for CAN bus to transfer signals. So do check the battery voltage first.

Then move on to check the electrical connection, wires, and battery terminals. If connections are lose, wire are borken or in bad conditions or terminals are corroded then battery will face difficulty to power CAN bus system.

If there is an short circuit or bad grounded connection then there will be problem in electric setup and thus problem with CAN bus system and trouble code U0101.

If these checkup does not solve problem then problem is complex to fix because it is completely a part of the circuit. if your try to solve problem with electronic circuit then there is a change that you may create more problems rather than fix it.

So, if you lack related technical knowledge and skills, then avoid this process and consult an expert mechanic.

How Much Does It Cost To Fix Code U0101?

As the causes of this diagnostic code are many and the fixing method is also not the same. For these different fixing methods, the cost is also not fixed and it is also almost impossible to give you an exact idea about cost. But you may require $100 to $1000 to fix this code. In this cost, the mechanic cost is included.

Code U0101 Lost Communication With TCM Infographic


The Code U0101 Lost Communication With TCM will become a serious issue for your vehicle’s transmission system if you don’t take it seriously. So, understanding this and solving is very essential. If you’re having trouble understanding or deciphering your car’s diagnostic Trouble Code U0101 take help from experts.

Thanks for reading from us. Some more discussions are there about the trouble codes on our site. You may read them too to enrich your knowledge.

Leave a Comment

Written By

Photo of author

William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

Fact Checked And Mechanically Reviewed By


Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.