The OK only means that you've entered a code that the Yamaha recognizes as being in its memory. That's unrelated to whether it's the right code.
I guess the only other thing to try is code search. I've seen that in some, but not all, Yamaha manuals.
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw