I recently moved from El Paso, TX (3762 ft altitude) to Texarkana (299 ft altitude)... and my check engine light came on. I was here about a year ago and had the same codes. When I went back to El Paso for a year I had no engine light or codes.... What could this mean? I dont know what to check.

 

First thing it to read the discription of the codes.
Not just a few words and miss interpet the codes. It's not the OX sensors!
Both codes are the same from both banks due to the same cause.
You have an air leak in the intake at some point that is marginal making the system sensitive to elevation pressure changes.
Check out all the rubber fittings and air hose connections around the intake manifold.
What has happened is the PCM has shifted the fuel tables to their extreme rich limits trying to correct for too much air from the leak.
When the tables are shifted to the limit, that sets the codes as the way the system has been given to tell you by CEL and codes that there is an issue.
Good lck.

 

How would I go about actually checking for leaks? I checked all the hoses that I can get my hands on and everything is tight. I am not really a mechanic... frustrated.

 

They get hard and crack over time or get soft.
You just have to get in there and feel what you can't see and make a judgement if anything does not feel right.
Look at anything attached to the intake that goes to vacuum.
large air hose around the mass air meter, throttle body gaskets, any place that would let 'unaccounted' for air in.
The MASS AIR meter in the large air hose has to measure all aiflow into the engine or it's 'unacounted' for.
It's there somewhere.
Good luck.

 

Sometimes when work is performed and the air intake assy from the air filter to throttle body has been removed it is reinstalled improperly. How do I know? I did it to my Mustang and had to buy a new intake tube. The seal area's near the hose clamps can mistakenly be rolled under when reinstalling the unit. The seal lip folds on itself and may work for a while till a crack develops allowing un-metered air into the throttle body.

 

Had the same 2 codes, 171-174 Took me forever to figure it out. Ended up being
a bad/clogged cat

 

common spot is the 3/16 or 1/4 inch vacuum hoses above the drivers side valve cover on 5.4 motor EGR. Hoses about 8 inches long. Pull each vacuum hose off one at a time and check to see if brittle, cracked, broken. Replace any small hoses as neede