Does reporgramming key Fob invalidate old keys?

[wdegregory]

Hi,

I am getting conflicting stories based on research on web and folks I talk to at dealerships and lock smiths. Bottom line, I have a 2015 Subaru Legacy with push to start and one of my Fobs was stolen and having a stolen fob out there worries me.

Ideally I get a replacement fob, reset entire immobilizer system and replace physical lock cylinders and cut new physical keys. But this is quoted at well over a thousand dollars.

So the compromise is to by an after market replacement fob and reprogram the 2 fobs I have to new codes (e.g., stolen key could be used to physically enter car but not start it). But I am told 2 stories, 1) that reprogramming a new key puts exact same codes on new key meaning the stolen key would still work and 2) reprogram uses new codes invalidating stolen key.

Option 2 is acceptable to me at about $200 and some change but only if this is what indeed happens. I don't want to pay $200 and still have a vulnerability with stolen key.

Can anyone way in with ground truth?

Also, called a couple vehicle locksmiths and none of them said they could take it on, does this mean my only recourse is the dealership?

Thanks. New to forum and first time poster.