the fact that your seatbelts dont work correctly and the airbag warning light is on only means one thing from the cars computer point of view that the car had a accident, rolled over or whatever, i dont know how qualified are those denters, if you are satisfied by the denters then in your mind just ignore the airbag warning light then.
about the check engine light, did you note the error code number that came up? if you tell the error code number only then it will be possible to help meaningfully, "exhaust switch" doesnt give much info to give advise on.