I guess I will just remain a bit confused.

If they indicated that they had removed the old sensor, replaced it, AND did all the other upgrades (to jack the price), then it would make sense to me.

But, I don't understand how a coach that evidently didn't have a sensor and worked just fine for some long period of time, started generating codes that didn't before, and adding a new sensor solved the problem.

Mark me as confused ...

Ray