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Key Programming - Better Safe Than Sorry?


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Hi Guys, my 1st post :)

Purchased a 2000 LS400 last month, VERY pleased! and finding these Forums extremely helpful but I do have a question I have been unable to find an answer for.

My car came with a "Master" key (with remote buttons) and a half key in a small plastic wallet with it's key code. Both keys are cut identically.

I was advised by an eBay locksmith to check my "Master" did actually turn off security light, immediatly I inserted it in ignition. This it did confirming it is the Master key? I have thus ordered a spare remote key and it is being cut. My plan is to follow the instructions on here to program that key and put my original away for safety.

My question is, if my current only working key is number 4 in the computer memory, do I risk bumping it out when I program my new key? I have no idea how many keys have ever been added and lost to this car in it's life, I do know from "My Lexus" it had to have a new ECU and Keys back in 2009 I'm guessing because keys were lost.

Don't want to repeat that expensive mistake :(

Thanks in anticipation, Phil

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Phil, according to the .pdf that Craig posted, you should be able to interrogate the system to find out how many keys are currently registered. And, even if you will go over four, the system will erase the oldest one and replace it. So, if your existing key gets 'erased', you just add it again and it erases the next oldest key on the list (which is probably lost...if there are even that many keys). It sounds like the key entry is 'rotating' so when you add a key it erases the oldest and replaces it. But you can only have four key codes active at any one time.

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;) Landar, Thanks for that, that is what I thought, I was just worried that as you need a "Master" to do the new key "Transponder Chip" teach to the Car (The Accelerator/Brake tap dance etc.) I was worried I might push my only master out of the current list if it was number 4!

Anyway I can confirm, a blank with remote buttons off eBay ($28), sent to another eBay member for laser cutting ($32) and using the two methods off here to a) Program new Key Transponder and b) Program new Key remote buttons. and I now have a fully operational spare "Master" that unlocks manually/remote everything (even opens windows/moonroof etc.) and starts car.

Very pleased and thank all contributers for the details :)

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  • 9 months later...

I searched high and low for key/transponder programming info for a 2004 SC430 and found anything from use the 2005 to a locksmith telling me they would "have" to do it, or the dealer is the only one for over $100 so for any one else running into this, I bought a cut key with guts and it came with the following.

And yes, I have always had someone sit in the passenger seat or driveway and read this off as I patted my head and scratched my *** to get this done. These may be specific to a 2004 SC430

Transponder chip programming- (Allows you to put a key in, turn it and then allows car to start)

1. Close all doors

2. Insert an already programmed master key into ignition.

3. Turn this first key from the OFF to ON and back (to OFF) 5 times.

4. Open and close the drivers door 6 times.

5. Remove the key (first key) from the ignition***

***After step 5 the security light should be solid "ON" If it is not go back to step one and start over.

6. Insert the new key (Second key) into ignition (DO NOT turn, just put in) for sixty seconds. The security light should be blinking for this sixty seconds and 

when it stops blinking the second key is programmed.

You now need to stop programming by pressing the break pedal once.

The security light will then flash for about a minute and then will go out.

Should now be able to remove key, and it will work as a normal key to start the car. Put it in, turn it and car starts. If not Repeat.


Remote Programming- (Not transponder to get key head to tell car to start but rather all the buttons on key head, lock-unlock-panic-trunk.)

1. Close and lock all doors. Unlock and open drivers door. Leave open and to to 2.

2. Put key (with the buttons that you want to program)  into ignition and remove it TWO TIMES.- then keep it out

3. Close and open the drivers door TWO times.

4. Put the key in ignition then remove

5. Close and open the drivers door TWO times then leave open.

6. Put key in ignition and then close the drivers door.

7. Now turn ignition ON and OFF -One time only.   (This puts the car into ADD mode for your new key remote buttons)***

***CAUTION Turning the key ON and OFF Two times will add the new remote buttons BUT erase all other prior key head buttons. 

8. Remove the key from ignition. The door locks will cycle (lock*unlock) {But will cycle twice if you are erasing all prior key head buttons}

9. On the key remote press and hold at the same time the LOCK and UNLOCK buttons for 1.5 seconds

10. On the REMOTE press the LOCK button for one second 

OR the lock and unlock buttons together at the same time.

11. At this point the locks should cycle by themselves ONE time this means procedure was accepted. (**if twice see below)

12. Open and close the drivers door and programming will end, your done and your key is ready to go.

**If not, programming has failed. Just start over and hold the remotes higher up for better reception.



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