I have a 1998 GS300 3.0L that the transponder chip fell out of the key and became misplaced indefinitely. I still have the metal key with empty plastic case and made new unprogrammed chipped copies from it, but the car is immobilized, and the locksmith guys couldn’t reflash the chip because the EEPROM or erasable chip hadn’t been made yet until 2001+. So I’m looking at buying a used year 2000 ecu with the corresponding master key on ebay to install and then transplanting the chip to my own key shank and case. I can’t find a ‘98 ecu with key so this is the most approximate I could find. I do think this will work, but there is a slight variance in the second half of the number on the ecu as expected from this type of part from year to year. To me, it seems they should essentially be identical. I know the (reflashable) 2001 ECUs don’t plug up right because of the pins, but will a year 2k ecu albeit with a slight variance in part number work okay for this application? I really sould like to know if my plan is fully sound, and I’d love to find a compatability chart if there is one. Help?

Many Thanks

Thanks for the reply! Not exactly sure what you mean by ‘funky’, but good to know that it’s more of a risk situation with that one. The problem still arises that I can’t find one within that year bracket of 98-99 that includes the key.

Might not be much help but my GS is a 98’ produced in 97’. When I had hesitation issues the replaced my ECU with a newer year ECU and used my existing keys. I think I did this sometime in 03’

Well, if it was a new ecu it wasn’t married to any transponder keys yet, so I’m sure it wasn’t difficult to reprogram your old keys to it.

The problem I’m facing is I haven’t been able to easily source an ecu that comes with the key. Every scrapyard and salvage parts place that I’ve called has every part of these cars including ecu, except the key. I’m looking at one for sale with the key, but it’s not cheap compared to every other offering, and I’m waiting for them to reply on my offer for a slightly better price. If not I’ll have to wait until I get paid tomorrow to go ahead and buy it. Somehow it all reminds me of the haggling scene in Monty Python’s Life of Brian.

edit: 01+ models have the EEPROM chip whose acronyms stand for Electrically Erasable Programmable Read-Only Module. I think Lexus was involved in a class action lawsuit for the pre-01’s being so involved in getting this sorted out, specifically without the dealer’s help. Which is also why they offer a “free” ecu once for a car if you lose the keys provided you buy new ones, which seems fair if you lost them. But in reality for me, the plastic case opened up and dropped the chip somewhere and I never saw it again, which I’m hesistant to accept blame for, either.

Thanks for the reply; and that’s a great suggestion, thanks. I’m new here so I will have to start looking for that subsection now!

edit; I’m too new. I think I need a moderator to give me marketplace posting privileges.

My understanding is you could never reprogram a 97-2000 ecu, not even once. What year model did you have it done on with the ebay reprogram method? I’m having the locksmith I used before coming to pick up my ecu and he says he’s taking it to a guy who believes he can make it happen. I want to think that with the current technology, maybe they really can program my unreflashable ic900 chip. If yours was within the same year spec as me, then I guess I might feel more confident about this tampering with the ecu to strongarm it into virgin mode again business Just not feeling very hopeful about the whole thing, but something will come along before I know it, and I’ll be back on the road, hopefully very soon!

Thanks, but I still feel like that option will get me closer to at least $500 service estimate, includng tow. Some people have had the work done for almost free while some get quoted upwards of $1000. Apparently some of those service writer guys just kinda pull the numbers out of...thin air.

You Tube

He does call the ic900 chip on the ecu board an eeprom, so I mostly dismissed it since it doesn’t actually apply to my car. I mean maybe you can dump the information on it to a computer, edit it, and put it back and it’s not necessarily the same as flashing it with hardware like the ezflasher or toyota’s own techstream software, but I would take his word that it’s an eeprom, and won’t try it myself. There is actually someone trying to do this to my ecu right now, locally, but I’m not too convinced it will work.

I read the item description, you need to send him a new ecu and your old ecu for him to program the keys. And nope, the locksmith guys who tried to hack my old ecu almost finally gave up, so i decided to just buy that key and ecu listing I saw on ebay. Only one I found with a key, which is funny considerig the ecu without its master key is essencially not usable... anyway, I’ll keep you guys posted in any case.

update;
I got the new ecu with key in the mail. It’s a 99 and my car is a 98. I think there’s a chip in the key cylinder assembly they supplied, but I tried installing just the ecu and seeing if anything would fire up. Apparently, it’s a lot more complicated than sticking in a new ecu, because it definitely didn’t even power the dash lights or the steering wheel adjustment welcome I get with my original ecu. I want to check if this ecu is good, but I feel like something is not letting it work on my car, not even letting me get interior power. I don’t know if these require vin programming but I read on another thread that usually these older lexus models do not. I’m not so sure what to believe anymore. I might have to start messing with the lock cylinder and swapping it maybe. The new one they sent me has a little electrical
box that goes to it and like, a little rubberized chip sitting tightly in an indentation on the outside of the lock. The guy who sold it to me said it would work as long as I “swap everything”. Maybe I should blindy just do it?

Hi everyone, I put the new ecu in and transferred the rubberized chip on the ignition switch and the little electric module that plugs into the sensor. The ecu chip is exactly the same as the one on my car, but I haven’t been able to get any power to the car with it. No dash lights or anything. Is there anybody with knowledge about these cars that can please help. I really hope the ecu I ordered isn’t shot. I also found the car has an immobilizer ecu. Could it possibly be rejecting the used ecu to the point it doesn’t even let me get power to the instrument panel, etc?