Check Engine Sign - Code P0138 - pops up summer time and goes away

When checking the code P0138, I found 4 or 5 probable causes and O2 sensor was one of them. How positive are you with this selection? I appreciate your answer. If I know for sure O2 sensor is the reason, it can certainly minimize my additional costs . Thanks

it can be sensor or circuit the cofe only lets u know what circuit is failing not what part to change. you need to read with a scanner or test manually.

How do I do this? Can you elaborate on this? All I know that code P0138 was displayed when checked with a scanner at Autozone. A little more in depth explanation will help me a lot. Thanks for your time.

you need to seek help on this matter