There's no reason you cannot change the fluid, but there's also no reason
to expect that it'll do anything to resolve your problems, either.
The transmission computer is putting the transmission in failsafe (3rd
gear only) and requesting the check engine lamp to be turned on because
it's detected some sort of problem. Each time you turn the car off and
on, it'll shift normally until it sees the problem again. If you're doing
mostly stop-and-go driving, you shouldn't continue to drive the vehicle
while it's in failsafe. Continued starting from 3rd gear can damage the