Two Fridays ago we had a very rainy and raw day here in New York. On my way back to work from lunch, my check engine light came on. When I got back to work, I took the gas cap off and put it back on. Four hours later when I went to work, the light was off. About a week later, we had another rainy day and after driving through a puddle the light came on again. I took it to AutoZone to be scanned. They gave me codes P2243 and P0134. They cleared the codes and the light came on again on a wet day.

AutoZone said the codes mean both O2 sensors need replacing. Is this true, or should just the upper one be changed?

Please advise...I an 99% sure I can change the upper one as it's right on the top of the engine. I'm not so sure about the one by the catalytic converter though.

Thank you in advance.