since june of 2006 ti have replaced the 4 gas cap 4 times causing the check engine light to come on emitting a code 422 i think also could be the reason for a code 455 as i recently replaced the 4th one on the car. cost should be between 12 and 20 dollars depending where you purchase it.

Gas cap cracked, but was surprisingly taken care of by dealership. Apparently the part is covered by an extended warranty due to known defects.