Programming a secondhand key - 2 button key (400h)

Yoda400 · June 9, 2021

Hi everyone, we have an rx400h which has two keys, one grey and one black. They are the two button keys, no power tailgate on ours.

I don't think the batteries in the keys have been changed for a while so I set about changing them to find that the head is stripped in the grey key. I think I'll get another key/case for that one. But it got me thinking that I'd like another one cutting so wife and I can both have a key and there will be a spare.

Anyway, without thinking too deeply, I bought a secondhand grey key from eBay that had the same numbers on the back of the key as my existing black key thinking that it would do the trick if I just get a new key blade cut for it and programme it. When I got it, the exterior of the case looked the same, but the key length is slightly shorter not that that should make a difference as I'll be getting another cut..

I opened it up to have a look at the transponder module and compare to the one in the black key. They look the same but the numbers on them are different, do they need to be the same to work?

Is there anywhere online that I can find out what modules are compatible with each other? I've searched high and low and can't seem to find anything...

So, in essence I've bought a secondhand transponder module which looks identical but the numbers on them differ. I should really just get a blank copy cut and stick the transponder in to try it but thought I'd ask on here first if anyone has done the same?

Many thanks

P.s. anyone know which key blank i should buy? My key blades measure 41mm from the plastic to the tip of the key, but I can only see blanks that are 38mm or 44mm in length?! Why isn't anything simple! 🙂

Superduner · June 10, 2021

You are about to dive into a rabbit's warren of obscure and mystifying sorcery!

Anyway, I bought a blank for my RX400H from Car Keys Online (car-keys-online.com). It wasn't too expensive.

Cutting the key can be done by most good high street key sellers. I'm not sure that many in the UK can programme them though. No key cutter here in France could programme the key to start the car - only to get into it without the alarm going off by selling me a cloned chip. I ended up going to Toyota to get it fully programmed (60€).

You will finds loads of posts and articles online (including this site) to tell you how to do it yourself. They involve intricate combinations of turning keys and locking and unlocking doors. For me, none of them worked, so I gave up and went to Toyota.

Spacewagon52 · June 10, 2021

I good independent locksmith will programme you one much cheaper than Lexus c.£150. Unfortunately you live the other side of the country, otherwise I could recommend a good one in Kent.

Yoda400 · June 10, 2021

Thanks for the info 🙂 I was hoping someone might have done the same in buying a secondhand fob to get a transponder out of it... I believe I might have to use Techstream to programme it. It does indeed appear a bit of a rabbit hole!

Herbie · June 10, 2021

4 hours ago, Yoda400 said:

Thanks for the info 🙂 I was hoping someone might have done the same in buying a secondhand fob to get a transponder out of it... I believe I might have to use Techstream to programme it. It does indeed appear a bit of a rabbit hole!

You need Techstream to program the immobiliser side of it and the black magic ritual to program the remote central locking - this Youtube video will help:

ColinBarber · June 11, 2021

10 hours ago, Herbie said:

and the black magic ritual to program the remote central locking

If you are using Techstream then just use if for the central locking part as well rather than messing with doors etc.

Herbie · June 11, 2021

8 minutes ago, ColinBarber said:

If you are using Techstream then just use if for the central locking part as well rather than messing with doors etc.

I'm not sure if Techstream can be used for that Colin. The video above shows the guy using it to program the immobiliser but the second half shows him doing the 'door dance' for the central locking. It just seems strange that if Techstream can do both, why didn't he use it for both? Unless, maybe he just wanted to demonstrate that it could be done without Techstream? I don't know?

Superduner · June 11, 2021

My local Lexus dealer used a system that I don't think was Techstream (but must have been similar). He programmed everything in about 5 minutes.

Yoda400 · June 29, 2021

Just to dig this up again as I've not properly got round to doing it, anyone managed to get a blank key for a two button 400h? I can't seem to find one!

The one I bought looks very similar apart from the key has a small ridge along it's length, I stupidly didn't spot this in the eBay advert but in it was well disguised by the seller 😞

Ridgeback · July 1, 2021

Rather than faff around programming a new chip, I cloned the existing black (master) key transponder chip, and copied the info to a special chip, so it was immediately ready to start the engine.

There are a couple of makes of remote keys (KEYDIY and XHORSE) that can be configured to 100's of different remotes, via a cable and phone app.

I configured one as a RX400h and programmed it to my 2007 RX400h with an Advanced Diagnostics AD100Pro.

This has to be diagnostically programmed, unlike the RX300 and most other Toyota/Lexus that are manually programmed by a series of opening/closing doors and ignition on/off.

I used one of the latest XHORSE remotes that is very similar to the Toyota Aygo/Corolla, so in addition to the 3 original remotes, I have a modern flip remote.

The cloned transponder chip fits inside the top of the XHORSE case.

I couldn't guarantee it would work with a 2 button, but most 2 button remotes are simply a 3 button circuit-board minus the boot button.

Most mobile auto-locksmiths will carry XHORSE remotes as part of their armoury, so these needn't cost a fortune.

Rather than trying acquire a remote from eBay that may be incorrect/faulty, ring around a few local auto-locksmiths and ask if they supply KEYDIY or XHORSE remotes, and how much it will be for yours.

Avoid the google search ads with freephone numbers that display first, these will invariably be the franchised chains that will take their fee and just pass on the job.