P0340 and P0134 on Dodge Neon ES 2001

Hey,

I have 2001 dodge neon with strange condition in its Check engine light. I have the check engine light "on" for couple of days and then it automatically goes off. It remains off for couple of days and then comes on again! This has been happening for last 5-6 months. Since it always went off I never bothered to have that shown to a mechanic. It has been driven close to 87,000 miles (mostly in Maine) and now in Dallas, Texas.
FYI - Car starts smoothly (with one key-turn), never felt like loss of engine power while driving etc!
I recently went to Autozone and they found P0340 (Camshaft sensor circuit malfunction) and P0134 (HO2S 11 circuit condition) associated code. I thank them for checking the code free of charge.
I have always suspected the fuel cap as one of the reason for the erratic check engine light! Am i right? Do i have any other option other than to take it to a mechanic (and thereby be victim to not-so-sure repairs that'll burn a hole in my pocket)?
Should i really worry as they check engine light keeps going off!!

I really appreciate any help/suggestion/answers based on your experience.

Thanks, Babs Mohan

gas cap has zip to do with those codes, probably just require anew cam sensor and a new 02, very common on those cars, get it fixed, you're fuel mileage will suffer because the cam is what times the injector pulse and a lazy 02 will lead to increased fuel consumption