2003 2.4t 147k
There are some threads on this topic but none for my situation exactly.
Coolant Low Stop engine warning once the engine is up to temperature.
Engine does not overheat, ever
Coolant is never low.
Yesterday replaced expansion bottle sensor, no change in situation.

Is there a float that can get stuck? How do you get to it?
Thanks for any possible advice.

 

Yes there is. You'd have to replace the whole reservoir.