P0128 Code 330Cic 26k low miles

I have a 06 330Cic with only 26k on the OD and got a P0128 Code. The vehicle is stored all winter Nov-May roughly 1/2 the year. I fill the tank with Shell gas (always use) and stable. The battery goes on a tender in my attached garage. So this year I bring it out and it throws a P0128 code.

I also should note that I knocked the cord loose on the tender and the orginal batter was dead as a doornail this spring. I fully charged it but it goes dead, so I replaced it, but the P0128 code was thrown the charged up old battery.

So, could old gas be causing the P0128? (We have Gov subsidised and mandated 10% Ethanol crap here) Could a weak battery, sitting all winter be any part of this code? Hard to believe the thermo is going bad, but if that's it, it's not showing any symptoms. It seems a little early for a cooling system, and it's not overheating, under temp is the code? Temp needle right in the middle and never anything strange going on with the temp.

I have a Innova CanOBD2 diag reader and pulled the code. The car and engine compartement are so clean you can eat off it. I don't even drive the car in the rain if it can be avoided to keep road spray out of the engine compartment. ( I know a lttle particular, but I drive a Camry appliance to work on the rough roads, stop and go rush hour, and avoid the road salt of winter here in Wisconsin).

So anyway, Any thoughts on the code or should I get busy doing the thermo (hard to believe at 26K?). Thanks in advance for any advice

Reb