Started having some battery issues about 3 weeks ago where I would have to jump when starting everytime. Tested alternator at home and read 13.8 so replaced battery. Evidently just got a good reading on alternator that day because 2 days ago car was dead again an hour away from home. Bought a new battery just to get me back to where it could be worked on and car was in limp mode not shifting out of 4th gear all the way home. After researching, I figured it was the low voltage from dead alternator causing issue. Changed alternator and all electrical systems are fine now, but the tranny is still in limp mode. Will get a slight rough idle upon starting but not other symptoms. No dash lights are on and only code that is being thrown is the P1778 Step Motor, but doesn't make any sense to me since the tranny was working fine before the alternator went out. Anyone ever experienced or have any thoughts? Just seems like a sensor but really not in position to just go buying sensors just for the heck of it.

 

is a 2008 3.5SE w CVT

 

The step motor is located in the valve body and more or less powers it. Could it have been damaged by the low and erratic voltage from the alternator?

 

I suppose that is very logical now that I understand what the step motor is. No way to know that without pulling the tranny correct?

 

Not the entire tranny, but the tranny pan underneath the car. Unfortunately, Nissan does not sell the step motor as a unit, they'd rather your bought the valve body.

 

what is the problem with my tranny why it want shift gears while I'm driving