I was gifted a 2004 S40. Had only one key fob. Went to a Volvo dealership. Cannot order a key, nor is it available nationwide (USA). I searched E-bay. A seller has a used key fob from a different S40 (roughly the same year), that looks identical to mine. The question is..... Can I purchase and use that key fob, from a different Volvo S40 vehicle, RE-PROGRAM IT AND CUT A NEW KEY, to work on my Volvo S40? Does that make sense?

 

Early s40 (99-04) with a metal key? (versus 2004+ with the plastic nub for a key)
You generally can't "re-program" a used remote for a Volvo in that year range. Well you can but a code that is needed for programming is only printed on the bag the remote comes in when new.

Do you have the "switchblade" style remote/key combo as shown below for 2003+? If so the plain key for a 2002 (#6 in the 2002 diagram) will work. Note that the steering column lock tumbler (#2) is the same part # for both years. The new key will have to be "programmed" using Vida to get the key to be accepted by the immobilizer.

If it were me simply looking for a spare key - I would order a precut 2002 style key from Volvo using your VIN. 3 days later it will arrive and if cut properly should open the door, trunk and turn in the steering column lock. That way if it's a bad cut - you won't have to pay for it. (I'm sure you might be able to find someone to copy your existing key onto a cheap ebay blank that might work - but then you will have to convince your dealer to try to pair your ebay key to your car.

If new Volvo precut key works - have your dealer (or anyone else with a VIDA subscription and a compatible DICE unit) "do a download" to program your immobilizer to accept the signal from your new key and allow the engine to start. Key and download will probably be ~$300