Actually, a code P1299, cylinder head overheat code. I researched it and found it sez a cooling system problem - thermo, temp sensor or head gaskets (no signs of bad gaskets though).
So I was going to replace both - there was plenty of water and oil.
Temp sensor on the computer side, not gauge?
Just out of the blue, for an otherwise trouble-free four years of ownwership.
Any thoughts?