I recently had to replace my remote, but I was unable to find anywhere on the Web the instructions for registering the remote unit with the car's computer. I eventually obtained the following instructions from an Infiniti Dealer and I have posted them below.

1.Get in & lock the doors2.Insert the key into the ignition 6 times within 15 seconds3.Hazard lights should flash4.Put key back into the ignition & turn to on position(do not start)5.Hit the lock button on the remote,hazards should flash.6.Press the master door lock (on drivers door arm rest) unlock/lock7.repeat step 5 and 6 for each additional remote. after last remote go to step 8.8.Pull key out and open the drivers door and then close it 9.It should be set

These instructions worked perfectly for me. If you have more than one remote, I believe that you repeat step 6 for each remote before performing step 8. However, I have not tried registering more than one remote.