Like people have said above pull the codes before you throw any more parts at it. Once you get the code(s) post it and im sure a group of people will have the "Ohhhhh thats the problem" light bulb go on in their mind. Once the code is set off, regardless of wether or not the light is still on, it is stored in the computer until it is cleared. Just remember not to assume, that is where mistakes are made and you will lose money if you just throw parts at customers cars. Diagnose it then throw parts at it, then if you are still wrong then it is a little more acceptable.