when I am traveling and I reach an elevation of 5000 ft and above my check engine light comes on. When I get back below the 5000 ft level and turn the truck off for 30 min. to an hour the light goes out. I have tried taken the truck to the dealer and they said the could not figure out what the problem was because when the check engine light goes out the code is no longer there. So I do not know how I am suppose to get my truck to the dealer with the light on. Does anyone know what could be causing this and what I might be able to replace myself that could fix this problem?