This code was there and the Trans is acting funny. Shifting to 3rd gear. Has anyone else solved and repaired this problem?

 

What is the code ?

 

U0101?

 

When asking for help please state the year engine size and mileage
Your code is a basic starting point but need more information!

 

2007 Mazda 3i the 2.3 with 137,000 miles on it

 

Ok so when was a standard oil and filter services were done on your Mazda's transmission?
*Has there been any previous or unusual shifting changes or any other operation like during cold starts and driving?
Did you recently change your battery if not how old is it from the time you purchased the battery. Month and miles?
Who retrieved the DTC if it was you what device specifically was used?
*acting funny and supposedly going to 3rd (from what precious gear) is not a very good description!