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The key has a RF (radio frequency) chip in it that uses a certain frequency. These frequencies are registered with the Federal Communications Commission (FCC) that gives a registration number (FCC ID) to the manufacturer. For the 2nd gen RX, the FCC ID is HYQ12BBT. This code is programmed into the transponder key ecu and the key has to match the ecu.
This ID code is marked on the key by most reputable manufacturers. To see this on the Lexus made key, open the cover (small philips screw) and look on the actual keyfob. On non-Lexus made keys, it could be in a different location.
DenniMik, thank you and I am aware of this information. Having purchased an aftermarket key from this vendor before for my RX300 that worked just fine, I figured I would try them again. The 2008 RX 350 transponder chip show to be 4D / ID 4D67. It is one of the most common transponder chips ever used.
Here's the Update:
I did bring the keys to a locksmith. He confirmed the chip was correct, but still could not get the unit to "confirm" a programmed key Fob and it would not start the vehicle. He did get the key Fob to unlock the doors remotely, but NOT the automatic rear hatch.
I contacted the seller who goes by "Elfe-Key" on eBay. They instructed me to take the chip out of my OEM Lexus and replace it with their aftermarket. I did this and the Lexus OEM key fob with the aftermarket chip worked!
I contacted the seller hoping that this would tell them what the problem was. However, once I contacted them, they told me that they don't have a solution???? I have no idea why he would have asked me to remove the chips unless he had a solution... To me, this would suggest whatever the base fob electronics are, they are not communicating with the 4D chip.
So now I have two useless keyfobs which can only open doors.
