Originally Posted by P10 WRC

will a four button fob work if my car came with a three button fob? i have an 06 sedan 6MT

Originally Posted by felixsc300

I have the four-button 07+ Intelligent Key remote that's been retrofitted with the guys from the plasticky key fob on the earlier years. A member did it for me on the forums, but not sure if he still offers that service. Key itself was $35, the service was $50. Total $85 with a one-week turnaround time, so you'll be keyless-entryless during that time.

In other words, if you just buy the key fob it will not work, but if you're willing to do a bit of soldering (or hire someone, like I did) then you can integrate both pieces into one.