Hello all,

I currently only have one lexus rx 300 key (which is a master key). I had been looking to get a new key but they are quite expensive, so what I ended up doing is buying an uncut key with a used transponder in it (also a master). I've seen some methods of programming master keys here on the forum, but I am now thinking I may have made a mistake buying a used transponder that may have been programmed to another RX 300. Can a used transponder key be reprogrammed to a different RX 300?

Thanks in advance,
Mike

 

You can have up to 4 transmitters on each rx300

 

Thanks for the response. Didn't quite get that though is that a YES or a No on reprogramming a used transponder that may have been programmed to another rx 300?

 

You're not 'reprogramming' the transponder; you are programming your car to recognize that transponder. So I believe the answer is 'yes.'

 

Nice info. To be clear these keys contain a 3 button transmitter AND a cheap (simple) RFID chip.It is the presence of the RFID chip held next to the key in the ignition switch that allows the car to start.
This type of RFID is excited by the car's receiver whereupon it transmits a unique number. The car's computer looks to see if that number is one of the ones programmed into the car to allow it to start. If not programmed then the car does not start.

Drcoffee gave you the programming instructions. I did this myself a few years back and it works fine. good luck

 

I'm confused....
I just did this and it put the car into prohibition mode. Now the keys don't work. How do I reregister the keys???

 

Did you try going into rewrite mode to re-register your keys?

 

Luckily I did the same procedure again and then held down the transponder for the three seconds the lock and unlock on the transponder at the end and it reprogrammed it so it works again thank God but the security light is still not working it comes on if I have the emergency key pressed ... so I know the light works but I think there's an issue with the immobilizer... And I can't figure it out