How Do I Program My Porsche Key? I Have A 2003 Porsche Turbo And I Replaced The Battery. Now It Won't Lock/unlock.

Well, you can sometime catch the code again. Pt the key in the ignition and turn till the dash light come on (don't Start) then press and the Lock button while keeping the Lock button Pressed and turn the dash light off and put the key with the lock button Press for 10 second afterwards. If not successful first time try again. This should do it.
Regards
Mark R
Southend