U0101: Lost communication with transmission control module

What does it mean?

System

Network (communication between control units)

Type of code

Generic code: means the same on every make.

How urgent?

Have it checked soon. You can usually still drive, but avoid long trips and heavy loads.

Possible causes

• Weak battery or an alternator not charging well
• Poor ground connection or damaged wiring
• Corrosion or moisture in a connector
• Control unit or software

Tip: don’t just clear the code. Clearing a code doesn’t fix the cause. It often comes back, and the stored data that helps us find the cause is then gone.