U0101: Lost Communication With TCM
Modules lost contact with the transmission computer.
Green, yellow, red: three ways U0101 can look
The same code can be a quick fix or a reason to pull over. Match your situation to the closest example.
Keep an eye on it
Logged once.
Schedule a repair
Shifting problems. Diagnose soon.
Stop and get help
Limp mode or no gear. Tow it.
Symptoms you might notice
- Limp mode
- Harsh shifting
- Gear display blank
Common causes, cheapest first
- Battery or ground problem
- TCM fuse
- Network wiring
- Failed transmission computer
What you can check before calling
- Check battery and grounds
A code points to a system, not a part. Replacing parts based on the code alone is how people spend money without fixing the problem. Testing confirms the cause first.
Generic codes (second character 0) mean the same thing on every vehicle. Some manufacturers add their own details, so check service information for your exact vehicle.
More network & modules codes
Look up another code
Cummins fault code (like 1922), J1939 SPN and FMI (like SPN 3251 FMI 0), or an OBD-II code (like P0420).
Questions
What does U0101 mean?
U0101 means "Lost Communication With TCM". Modules lost contact with the transmission computer.
Can I drive with code U0101?
It depends on what the vehicle is doing. Green: Logged once. Yellow: Shifting problems. Diagnose soon. Red: Limp mode or no gear. Tow it.
What causes U0101?
The most common causes are: battery or ground problem; tCM fuse; network wiring.
Is U0101 a serious code?
It can be. Limp mode or no gear. Tow it.
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