Nissan sunny car 2005 with auto transmission my car is stucking in second gear for few seconds during my 20km trip it will stuck one time then it will not moving more than 40 speed so what symptoms i changed transmission fluid.i can prefer to repair auto transmission unit or i need to change complete unit please suggest me thanks.
It sounds exactly like your car has switched into emergency mode after an error had been detected. The limited speed allows to arrive to the service safely. The solution may be plugging in the diagnostic device to the on-board computer and deleting the errors. The devices are really expensive, so i recommend to use service of mechanical service which ownes one.
The emergency mode may have been caused by various reasons. In my W168 Mercedes the same problem has been caused, as i've been told, by malfunction of gearbox's control unit which been constantly generating error and causing emergency mode. I've heard about a guy who repaired the same CU on his own, but unfortunately my mechanic seen only solution in replacing the whole unit.