LS430 Transponder Key Computer - key fob related

Redefined · January 31, 2023

Just thought I'd post this up as it might help answer someones question or perplexity with their own keys/remotes. Background of the story is that I got the 2001 model a few months ago and it came with 3 sets of spare key shells. This leads me to (now) understand how there had been lots of attempts or intentions at fixing this here problem.

The problem being that the actual remote buttons on the keys don't work but the radar sensor does. Some research on the forums and from Car Care Nut' channel on YouTube and I've determined that there is 2 systems at work in the key fob. One is the proximity/radar sensor and the other is the actual immobiliser. I'll not go into much depth as it's complex and I don't fully understand it.

However, what we do know is that one system uses the remote key Battery and the other does not (I think). This is what probably explains how I can just get into the car without a Battery in the remote and start it up with the plastic prong into the ignition! More info on alarm types on these super complex structures here -

From this vid I've kindof ascertained that the LS430 system is probably closest to the 04MY Prius. One that CCN describes as, 'not the best'.

Right, so after a bit of exploration without the remote Battery in the key I can confirm that I will still be able to use it. This is by pulling out the key which would need a properly intact plastic-casing. Because when you pull out the key out of the casing theres a prong that locks it into place so you can engage the key into the door lock (without it constantly pressing back into the remote case).

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Before going any further, I think I should include that I spoke to Lexus earlier about the keys. £131 + vat but this doesn't include coding. How much for coding I asked the parts chap (who was nice) who indicated, 'how long's a piece of string'. Not in them words but basically that he wasn't sure how long it would take for coding such an old key and that maybe I should see an auto-locksmith.

One call later to someone that 'don't work on Lexus', but pointed me to AC autolocksmiths I was informed that it's the Transponder Key Computer. He doesn't work on them but its basically the computer that is finding it hard to see the signal from the key. Obviously (I checked, the part is about £500) I'll not be going down that route and hence and making this post for info purposes.

More to come in post 2 below:

1. How I can access the boot with the key.

2. What I mustn't do when accessing the car with the actual key and manual lock.

3. Why I need to order a secondary plastic sleeve for the key...

4. Whatever else I can think of (like my initial symptoms and how I get into the car at present using the transponder/immobiliser method).

BigBoomer · January 31, 2023

It might help if you could post a photo of your key as there are 2 different key types for the LS430 and they work in slightly different ways.

The remote (radio) part works via 433Mhz (UK & EU) and requires a Battery as it is transmitting over several yards distance. If you push the button on the key, it transmits a signal to the car which then has a little chat with the key resulting (in a few milliseconds) in the car accepting that it is a valid key and unlocking/locking the car (or opening the boot).

The immobiliser system works via the unpowered RFID (Radio Frequency IDentification). When you push the key into the ignition there is communication between the car and the key and if the key is the correct one, it allows you to turn the switch and start the car. RFID is like the chip in your Contactless bank card.

If you have a "SmartKey" as came with the 02-06 models, then that second RFID part is also handled via the first (433Mhz) communication so you never have to take the key out of your pocket. The car "pings" for the key every second or so, and as you approach the car the key responds, they talk, and it validates the key. This is when the interior lights come on.
When you touch the door handle it unlocks the car so that you can enter.
When you push in the ignition switch (without the SmartKey in it) it validates the key again before allowing you to start the car.

If your SmartKey Battery is flat as a pancake you can still use the RFID part independently of the 433Mhz part by pushing the plastic key into the ignition switch.

Redefined · January 31, 2023

Thanks @BigBoomer good point...

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BigBoomer · February 1, 2023

Yup. SmartKeys and they appear to be the master keys as the valet key does not have the boot button.
You really need to have 2 keys anyways, so I would recommend getting one from a Lexus/Toyota dealer and have them program it for your car.
If you lose the key or it completely stops working then you are in for some serious bills.
No, the SmartKeys are not cheap, but then this was a £60,000 limo when new 22 years ago so parts are always going to be pricy.
Since your existing key is not working normally, that could be a problem with the key, or a problem with the key computer.
The cheapest way to find out is to get a 2nd key. If that works normally, then it was just the old key.

Redefined · February 1, 2023

Thanks big boomer. Thankfully both them keys work on the radar/proximity sensor but not the actual buttons. Pressing the buttons on either does nothing except for flash lights in the keys. Speaking to the autoelectrician key guy and explaining the symptoms he seemed confident it's the reciever unit.

Just spoken to another Lexus (Sheffield) today and got a full price of key + coding. Leeds for some reason were unsure about how long it would take to code a key so couldn't give a price. £190 including coding +VAT on top. He did say that it might not cure the problem and that diagnostics would cost £135 to plug in their computer.

Hence why I think I'll just continue as is (with the proximity unlocking) and when the keys start dying further I'll just convert it all to manual lock/unlock. Especially since the keys still start the car with Battery out by plugging the trandponder key into the lock.

Micholas · February 1, 2023

I am also down to one key, and it’s the master key. My key & smart lock system is very temperamental. I’ve queried getting a new key every time I service the car, but always get told there’s huge delays with spare key orders due to the microchip issues in the world. They quoted me approx £300-£350 and said I might see it in 4-6 months. I’ve never taken them up on that offer!