So here we go...today while driving I was experiencing no problems at all in my 2010 mazda 3 sedan. I stopped at a park to eat my lunch. Upon returning to my vehicle i noticed my check engine light was on along with the AT light. I started my car and tried to drive away and no RPM's were being engaged. i towed my car back home and put the code reader on it. U0101 popped up. I did my research and found that it is the Transmission Control Module. After searching the web for another couple hours to see how much it would cost and also looking for DIY videos I was certain that this was a fix that I could do...

Well here is where it gets strange, I go back to my car and turn it on to find that now No check engine light is on, no AT light is on and it's running perfectly fine. I drove the car around my neighborhood to no problems. I am baffled at this point and dont trust it at all. i need help, what has happened? Is this normal?

 

U0101 is a communication fault code between the PCM & TCM.

1 thing that can cause it is low battery voltage on cranking.

Get your battery tested.