Go to your local dealer an talk to a service rep give him your car vin no. and have him run for you. It worked for me, I found out that mine was already changed they even gave me a print-out of all the parts by no. description of the work labor time etc. very complete. Don't cost a thing but time, if you are to far from the dealer call 1-800 for merc and ask them, have your vin. no. ready.