Trouble code · Network · Generic (all makes)

U0101 Lost Communication With TCM

Another computer in the car can't talk to the transmission control module (TCM) over the car's network.

Safe to drive?
Drive with caution
Get it fixed soon
Scanner you need
Multi-system scanner
A basic reader isn’t enough
NHTSA complaints quoting it
54
Vehicle complaints, 2015–2025

Common causes

  • Weak battery or poor ground connections
  • Damaged network wiring or connectors
  • Blown fuse to the transmission computer
  • Failed transmission computer

Symptoms

  • Limp mode or stuck in one gear
  • Harsh shifting
  • Gear indicator blank
  • Other warning lights

Can I drive with it?

Drive only if it shifts normally, and get it checked soon. If it's stuck in one gear, avoid highways.

Tip: Check the battery and the fuses for the transmission computer before suspecting the module itself.

Which scanner reads it?

Many basic code readers only show P codes. Reading U codes – and seeing which module stored this one – needs a multi-system scanner.

See ABS, Airbag and Transmission Codes for which tools read each system. Not sure which fits you? Try the Find My Scanner quiz.

In the data

Of the vehicle complaints owners filed with NHTSA from 2015 to 2025, 54 quote U0101 – most often from Chevrolet, Ford, Dodge owners. Complaints lean toward serious problems, so treat this as a sign of how often the code turns up in real reports, not how often cars get it.

Both sources are compared on the Trends page.

General information to help you understand a code – not a diagnosis. Your car’s service information or a qualified mechanic has the final word. See how we research.