I drive a 2003 Mitsubishi Montero Sport. A few months ago the check engine light came on. I had it checked out and was told it was the catalytic converter. Well, the light went off and I never did anything. However, it occassionally comes on when it’s cold out. I live in San Antonio so it’s not really all that cold relatively speaking. A little history - last summer the light came on and it was the O2 sensor and it was replaced. What should I do? How important is fixing it? I probably drive 300-350 miles a week (about 250 highway miles).
If you have less then 80k on the truck, the cat is covered under the federal emissions warranty and should be covered at the dealer if the light comes back on. Otherwise, go to a muffler shop and get an aftermarket installed.
Don’t get anything replaced unless you have a proper diagnostic performed, by a person, not just by a machine. A trouble code, like P0318, isn’t a proper diagnosis.
If you are not subject to emissions testing, this is not a pressing issue. Getting a freebie out of the dealer is a lot easier said than done. Usually, you must fail an emissions test before they are required to do anything.