I've got a 5.9l 360 Dodge Ram, 1500, and the check engine light keeps coming on.?

Took it to a shop, had a diagnostic scan done, was told it was the gas cap being loose. Reset the computer, and sent me on my way. It came back on the next day.
I'm wondering, would the oxygen sensor have anything to do with this? It's due a new one in 200 miles.