Actually, at least on my 2010, after following the programming steps with my new fob, the old one stopped working. I had to go through the steps again and program both of them at the same time since entering the program mode apparently erased all of the prior key fobs. That is good if a fob was lost, then only the good fobs will work. I would just have both with you and program both at the same time. Once one is programmed, you can just immediately press the buttons on the other fob and it will register.
And the instructions are in the owners manual and here:
viewtopic.php?f=18&t=35953&p=402298&hil ... ob#p402298" onclick="window.open(this.href);return false;
I read through the thread and, and it does appear that there are several programming modes. Might read through it and try it out.
Good luck.