here is a link for reflashing the 3UZ ECU and disabling the immobilizer
and this link will will show you how it’s done on the 1UZ VVTi or the 2JZ for all the folks with the looong block option!

 

Well John i did find another transponder amplifier and tried to switch them out to no avail, I'm thinking the ecu is the problem, maybe a loose solder joint or something on the immobilizer location which i think is ic900. I'm very willing to go the route you did with the remapping, the battery disconnection is the least of my worries. Just wondering how you found you're guy? what do i look for or ask? I've tried a couple in the past and they always say they dont have lexus software.

 

thanks for the info dwoods,,looks complicated,haha

 

make sure to like any posts that u like, it’s the only compensation I will ever that won’t effect my taxes

 

Honestly, I ended up fixing this by going to ebay and buying a new ECU/master key combination for under $200. It was literally a 10 minute swap. The gentleman on ebay specializes in this sort of thing and tests the ECU (it's used) fully as well as pairs it with the new master key.
It's been running flawlessly since then. Assume it's just an intermittent failure on the main ECU board particularly with the fact that the car at this point is over 20 years old.

Scott

 

scott802 Thanks for the response, i think i may try out this one group of people australia i think and they have a place here in the states where you can send your ecu too and they simply disable the immobilizer. I will let you know how it goes.

 

hey had the same issue .. car would start pretty much when it wanted too. lol.. checked continuity from connector on key switch amplifier to ecu .. all wires have continuity .. inspect connector on amplifier .. found female side pins way to opened .. and causing bad contact with male pins .. closed female pins to create better contac with male pins .. car started right away .. immobilezer light turnned off right away when key was inserted into switch ..

 

bernalj- Interesting, i got another amplifier and key ring from a gs300 in good condition and swapped them out separately but to no avail. Is the female part of the connector on the car side? Thanks, ill give it a try before i get the immobilizer disabled.

 

hi bernalj,
I have the same issue and just read your solution of closing female pins which you posted over a year ago and I wanted to ask if it was a permanent solution to for you.
thanks!

 

There are several companies rebuilding the ECU’s for any Lexus. I believe one of the better known options is Phoenix Engine Management. They can rebuild them, and they offer several options like deleting the immobilizer, altering the rev limiter, or changing the tune to improve performance or gas mileage. They even have a “pops and bangs” tune that looks like a lot of fun. If you wanted them to do everything on the menu to a 2JZ or 1UZ/3UZ the total cost is around $500. If you haven’t had your ecu serviced, then you should look into it. If you wait till the capacitors start leaking then you will have to find a replacement and if you go used, you’ll want to get it serviced before using it.

 

**update** Well i sent out my ecu to a company out of texas and he found some leaking capacitors and re installed driver, it fixed my random no start problem with immobilizer . He even "forgot" to disable the immobilizer since he actually fixed it, then he offered to take it out if i still wanted but i told him no because that was my desperate attempt to not deal with the immobilizer but now i have a refreshed more "secure" gs300.

Thanks everyone for the ideas and support.

Dwoods801, maybe i will check out that company later for one of those tunes when i get a new car and have this one as a backup.

 

I don’t know that the GS300 has that much potential improvement can be found thru a different tune. The 3UZ is the engine that the engineers left tons of improvement trapped in the ECU. I know they gave the 4.3 the same 300hp rating as the 4.0, which was strange. But I am now certain it can be accessed and it’s worth the cost. You’ll want investigate this more, and see what results other GS300 owners got. But it’s good to learn that your problems were resolved. These capacitors are a nuisance, I had replace one in my home HVAC compressor a month ago cause it was leaking.

 

Phantomgray, can you post a link or the name of the place who serviced your ECU? The immobilizer in my GS400 is starting to lock me out randomly, and the it's happening more and more often, so I'd be thrilled to find a place that can refurbish my ECU, and also delete the immobilizer. Thank you!

 

Yup, i will message you right now.

 

Would a bad ECU still let the car crank? Or does it not crank at all in all of these cases? Mine isn't even cranking.
I was letting my car warm up the other day with the remote start and when I got in it I pressed the windshield wiper button and the car shut off. Now it won't even crank when I try to start it, but the car still has power. I checked the ignition fuses and relay, theyre all good. I even tried closing the starter circuit with a wire which caused the starter to crank, but still didn't start the car, so I know the starter isn't bad.
The car had an aftermarket alarm/remote start system, which I thought may be the issue, but I've since removed all the wires going from that to the ignition cylinder to rule that out, and it still won't even crank. It seems like there's no power going to the starter from the ignition cylinder.
Anyone know of any other tests or things I could do to troubleshoot this?