keyfobs

Hi all My question is,i bought a Lexus fob from ebay 3 button, i have programmed the fob to work with the immoblizer, but it will not program the fob to work with the central locking. Is there diffent internals to the Lexus fobs or are they all the same or can you use the internals of a Toyota,i have search the Lexus Forum and found the correct info but will not program the fob. Thx inadvance Ste