1211 code both banks

okay i changed the o2 sensors...was going to play with the MAF next but then i drove the car when it was cooler outside the other night...lights went out so i checked coolant level and it was a bit low so i added fluid. the lights stayed out for 2 days..after sitting in some traffic they came back on....started driving and as temp of car dropped below 195 they went off... if it is cold out they dont come on if its hot out tand car is warmed up the lights are back?

so what is the deal here? seems like it is a temp sensor issue??