I'm assuming you aren't doing the standard (non-Tech-2) procedure to add a fob that's in the owner's manual.
There are two procedures to add a fob using a Tech-2.
The first adds a new fob and deletes any others that have been assigned to the car. You can do this, but will have to add the second fob as well.
The second procedure is used when a new RCDLR is installed and new fobs are added. It also requires a TechLine connection, found at a dealership.
Here's the first Tech-2 procedure:
1) The vehicle must be OFF.
2) Open the glove box.
3) place the new, unrecognized fob in the glove box slot with the buttons facing to the right.
4) Connect the Tech-2.
5) Access the Module Replacement/Setup
under Vehicle Control Systems
. Select Program Key Fobs
. Follow the onscreen instructions.
6) Select Program Key Fob X
(X=1,2,3 or 4) depending on which fob you want to introduce to the RCDLR. Follow the onscreen instructions. Once this step is complete, the previously registered fob is erased.
7) Repeat for any additional fobs.
8) Disconnect the Tech-2.
9) Operate the fobs to ensure proper operation.
10) Have a beer for each fob successfully registered.