Have a 2002 with 34,000 miles on it. About 2,000 miles ago had a CEL with a code of P01456. Checked the gas cap and it was loose. Tightened the cap and re-set the code (code reader was well worth the 0 it cost). Today had an emissions light with a code of P0134; indicates an O2 sensor problem. Again found the gas cap loose. Examination of the cap does not reveal any problem with the cap. The cap is always tightened more than 3 clicks yet the cap has been found loose twice. Under what conditions, if any, will the cap work loose? Thanks for any help with this puzzler.