OBD2 Car ScannerWhat does U0101 mean?
U0101 stands for Lost Communication with TCM. Two or more of the car's computer modules are not communicating properly over the vehicle network (CAN bus).
Network codes cover the communication between the car's computer modules. When the car's computer sees a reading outside its normal range, it stores this code and may turn on a warning light on the dashboard.
Common causes
- Low or weak battery
- Damaged network wiring or connector
- A module that has lost power or failed
- Aftermarket accessories interfering with the network
What to do
- Read all stored and pending codes with a scanner. Several codes together often point to one cause.
- Note the freeze frame data (speed, temperature, load) recorded when the code was set.
- Inspect the wiring and connectors of the part named in the code for damage, corrosion or looseness.
- Fix the most likely and cheapest cause first, then clear the code and drive to see if it comes back.
Read this code from your own car
Plug in a cheap ELM327 adapter and the app shows every fault code, what it means and how to fix it.
Frequently asked questions
What does U0101 mean?
U0101 means “Lost Communication with TCM”. It belongs to the network communication group: Two or more of the car's computer modules are not communicating properly over the vehicle network (CAN bus).
Is it safe to drive with U0101?
You can usually drive carefully for a short time, but fix it soon to avoid further damage or higher fuel use.
How do I clear U0101?
Fix the cause, then clear the code with an OBD2 scanner or app. If the fault is still there, the code will come back.
Related codes
- U0071Vehicle Communication Bus E () High
- U0072Vehicle Communication Bus E () shorted to Bus E (+)
- U0073Control Module Communication Bus Off
- U0100Lost Communication With ECM/PCM A
- U0102Lost Communication with Transfer Case Control Module
- U0103Lost Communication With Gear Shift Control Module A
- U0104Lost Communication With Cruise Control Module
- U0105Lost Communication With Fuel Injector Control Module
Code meanings can vary by manufacturer. This page is general guidance, not a repair manual. Always confirm the cause before replacing parts.