I'm assuming that you have a wireless transmitter for the 5 already. There are a number of different wireless transmitters available for the 5. If the transmitter from the 3 matches the 5 it should work. You need to find the stamp on the inside of the transmitter (You can open it by pushing on the little tab in the groove where the key would be if closed.) If the codes match (they're pretty long) you should be able to program for the 5. Instructions for the programming are in the how-to section.
I do have a transmitter already for the 5, with the switchblade style key. I also have a plain key with no transmitter, as well as a separate fob from a 3 that I'd like to program to the 5.
Basically just wondering if, using the instructions for programming a transmitter for a 3 will work when trying to mate it to a 5.
Programming a key for the immobilizer and the remote transmitter are two separate operations so I imagine that the programming steps for the 5 to add a transmitter should work. Given the nature of the programming you'll know immediately if you're successful. If when you press any button on the 3 remote and the doors cycle you're good. If it doesn't cycle then push the button on your existing 5 remote to finish the programming with your existing transmitter.
I'd make sure you're able to program the transmitter back to the 3 as well just in case the programming for the 5 does something to it.
I'm assuming the 5 instructions are the way to go. By doing to pre-amble to the programming of the transmitters you're basically telling the car "Yes I'm your legitimate owner, I want you to accept the following keys"
If you followed the instructions for the 3 I doubt the 5 would know what to do.
