I have a 2006 Cooper S Convertible. Automatic transmission and I have the paddle shifters. Two months ago I started my car in the morning having no issues at all the day before or prior...the transmission stuck on 2nd gear with a check engine light and the code EP error, after clearing the code, it never came back and the car ran perfect...I read somewhere someone had same issue and did mention to check the battery, might cause this. yesterday leaving the restaurant with my wife the transmission stuck on 3rd gear, but no check engine light or EP error code. All I did is pulled over, shut the car off, restarted it and it's running perfect again. Could it be the battery??
I do connect small GPS and charge my phone at times. Also I use a battery tender in the winter to keep battery charged (maybe I shouldn't). Any thoughts.......Thank you.

 

Start your car, use a volt meter and check the voltage. It should read 12

14.0 to 14.2, if it does not, the alternator or battery may be at fault. Get the battery checked, to see if it is at end of life, if it is, buy something like interstate battery. Make sure it is a battery that is known to be stable. BMW electronics are very sensitive to power fluctuations.
If the alternator is going out, your best bet is an oem replacement.

 

Thank you...Any recommendation where should I go to get and OEM one?

 

I will take it to advanced auto or AutoZone to have the battery checked.