I had a Blank Chevy key hanging around that was a PK3 that I wanted to get cut to work with my CTS's door incase I locked myself out or something. I went to the dealership and had a genuine Cadillac PK3+ key cut, along with this Chevy PK3 key. The wierd thing, was that I was able to program the Chevy key to START my CTS. You're not supposed to be able and do that are you? What's the difference between the PK3 and PK3+ then?