zukikat

I'm trying to see if we can compile a list of which ECU part numbers would be found in which model years of SC300 and SC400 and maybe even with which options because I think that info would prove helpful to a lot of people, plus I really need some help asap, please!

I have a U.S. model (afaik) P/N 89661-24453 ECU, definitely OBD-II and I need to know what year it's from (for proper wiring diagrams) and more importantly whether or not it's got the whole "matched keys Lexus Immobilizer" system in it or not.
I did several Google and CL searches and couldn't find the answer and it shows up in Google as anywhere from a '96 - '98 SC400 at random which doesn't really help me.
One Google result claims the Lexus Immobilizer system first appeared in the 1997 LS400 and the SC400 in 1998 but I don't know if that's really correct?

This ECU, Engine Harness, Engine, and Transmission were bought together as a bundle and did NOT come from the 1993 SC400 they were dropped into by someone else.

I just inherited that 1993 SC400 project by its' previous owner with a "no fuel or spark" problem and found that there are extra harness connectors with nowhere to plug them into this 1993 SC400 and of course no OBD-II diagnostic connector in this OBD-I car, among other issues...

My challenge is this...
I believe the original "Security" system in the OBD-I SC's like any other OBD-I and prior Toyota vehicle is just a basic starter kill type "Theft Deterrant System" that has no effect on ignition (spark) or fuel at all, please correct me if I'm wrong?
I actually got the EFI Main relay to energize and got the fuel pump to run without even rigging anything so far but there's still no spark which I think is probably a matter of a mismatched connector and/or some sort of mismatched years of engine bay components issue.
I'm really hoping that this ECU is NOT an Immobilizer ECU because I know a '93 motor swap back into this 93 would certainly be an easy solution but I really don't want to have to track down a 93 motor, tranny, harness, and ecu and swap them out if it's just a matter of fixing a handful of wiring discrepancies to power this other ECU properly and maybe needing a few different engine bay components to make it run and then splice in an OBD-II connector into the car later if I decide it needs one which I think I can easily do if I can get the factory connector layout and pinout info for the car and this ECU to match everything up as needed.

Thanks in advance for any help that anyone can offer!

cartmill

iTrader: (3)

11/1995 - 08/1996
UZZ30 ECU

i'll help more with this when i get home from work.

cartmill

iTrader: (3)

1. i am about 90% sure the 95+ ECUs had immobilizers. so that's your problem right there. the ECU probably doesn't have a matching key (or who knows how much other OBDII missing stuff) so it won't let the engine run.
2. IIRC, the 95-97 had a removable immobilizer chip, and the 98+ had it built into both the ECU and immobilizer unit behind the ignition/key area.

3. you could try to get a wiring harness and ECU from a 93, but there will still be some things different on the engine (i dont know exactly what though). the actual engine should be pretty similar between 94 and 95, but i know there was a horsepower increase on the 95 and several other things. some of the sc400 guys need to chime in here...

i think your best bet is to get a 92-94 harness and ECU. these things are a dime a dozen, and they will match up to your car. i think this would match up to your body harness and at least get the engine running. swapping wiring harnesses on the 1uz is a complete PITA though, especially with the engine in the car. just get a 94-92 harness/ecu, pull that engine/harness/ecu out and start completely over

zukikat

Thanks for the info, it's greatly appreciated!

So that part number of ECU appears to translate to a 1996 model then, based on those vehicle production dates?

I don't think the actual 95 model is so different from the 94 and older as most wiring diagrams I can find online so far seem to go up to 95 and then switch to an 8-channel injector system for 1996 instead of the 4-channel injector system the OBD-I V8 Lexus cars use. Typically 1996 was the OBD-II transition year for most vehicles but there were some exceptions and I don't know for sure what year that was for the SC's...

Not to wander too far OT from the Which ECU P/N's for which years of SC's in this post, but...

I'll bet that your 99 SC300 has the 3-button remote built into the head of the "transponder key" with the immobilizer system as standard equipment but I don't know what year the 3-button remote was introduced. I suspect that whatever year Lexus switched from the single-button in-key remote to the 3-button version is the year the immobilizer was introduced.
Prior to that, the single-button remote was just a "starter kill" system afaik and the removeable chip was actually in the remote entry receiver unit and simply stored the remote codes for the specific remotes to work but the keys weren't chipped and transpondered at all in that system.

After days of searching I had read somewhere online that the immobilizer system was first introduced in the LS400 in 1997 and then other Lexus models like the SC in the following model year which in theory means the 1998 SC's were the first SC's that got it but I don't know for sure if that's correct or not.
If that's the case and your date info for my ECU is correct then it's NOT an immobilizer ECU which would be awesome.

I know the remote entry receiver for the security system in the 93 SC has a removable chip in it that actually codes the remote entry system to a matched pair of remotes but that's not the same as the immobilizer system, that's just for the remote codes. I know that because I just replaced that chip in my 94 LS (which uses that same remote system) to go with the new pair of in-key remotes the new receiver code chip came with and the car itself doesn't know one key from another and will start with any Lexus or generic key blank as long as the cut is right for the car's keyholes.
Plus I replaced the main Engine/Tranny ECU in my LS and it couldn't care less that I'm still using my same old keys.

Part of the challenge I have with all this is that I'm a looooong time Supra owner of all 4 generations of Supras and the early Celicas back to the carbureted days with a couple of 2nd and 3rd gen I4 and V6 Camry's and an 1st and 2nd year Lexus IS300's and now a final year 1st gen LS400 in the mix and a buddy's wife's 2000 SC300 too but most of my Toyota anti-theft knowledge is based on what Toyota did in the Supras with the original Theft Deterrant "Security" System and then the TDSE Security system add-in Remote Entry "Enhancement" kit with glass disturbance/breakage sound sensor, and my EMS knowledge is mostly based on the transition into OBD-I during the 3rd gen Supras and then to OBD-II within the 4th gen Supras and so on and so on...

So the "when and how" of Lexus is really similar in design to what I'm already used to in the Toyotas but it doesn't always parallel model year changes with the Toyotas I'm more familiar with.

Believe it or not I just installed a "Data Link" diagnostic port OBD-II check connector into the 93 SC400 that I scavenged out of a junkyard car and this OBD-II ECU actually reported the P1300 and P1305 igniter circuit 1 and 2 malfunction codes which steered me to check for problems at the igniter connectors and revealed to me that the ignition system's B+ power feed isn't getting to the coils or the igniters at all.
I then tried to reset the ECU with the reader which also worked and re-scanned and got the all-clear with no codes, then tried to start the car again and then re-scanned again and those same two codes came back so my new connector works great! Installing the connector was as simple as a power wire, 2 ground wires, and the data wire to the proper pin on the ECU, I'm so glad that actually worked!

I presume there are OBD-II codes for if the Immobilizer is triggered on cars that have it?

cartmill

iTrader: (3)

guy, what i am saying is that i think all 95+ SCs had an immobilizer.

but the 98+ immobilizer is the standard "built into the ECU" one like you're thinking.

yes, the dates i posted translate to "late 95, early 96" all 96 model year.
late 95 is when these cars got their first round of "updating," which involved obd2 and, an immobilizer (the one that's NOT built into the ECU) tail lights, black leather interior, and all kinds of other crap

zukikat

I guess I'll have to take a closer look at the 95 SC400 that's sitting one row over from the 92 in our local junkyard then as both of them still have their engines and harnesses and ECU's and such still fully intact with the usual gauge cluster and stereo and fuses and door panels and switches and piddly little crap long gone as is usually the case...

Not to sound all stubborn like I don't hear and appreciate what you're trying to tell me because you're definitely providing helpful information to me about the model years that I don't know and I do totally thank you for all the help and insight you're providing, but if there's an immobilizer system that's not built into the ECU, especially if this 93 SC wouldn't have gotten it, then unless there was some sort of secret initialization handshake data signal between it and this 96 ECU that keeps the ECU on some sort of lockdown without the presence of that signal (which so far the OBD-II system isn't reporting to be the case) and it's not just a pin to low or pin to high switching command on an ECU input pin and I can't find a way to emulate such a signal if that is the case, then otherwise so far I'm still confident that it really shouldn't effect this project beyond the potential need for a minor wiring work-around with it being prior to that super fancy 98+ ECU embedded transponder system, although we'll definitely know more about this once I see the Lexus wiring book for the 96 model year.
Twice over the years I've stared at the wiring books and gotten around older factory Toyota security computers when the car wouldn't even crank due to the very rare occurrance of a failed factory security ECU and I did it in both cases without any harness hacking and the cars both stayed that way and were totally drivable as-is while a used stock replacement for the failed security system ECU could be located and installed, so as long as there's no key specific and/or transponder type system embedded in this mix and it's sounding more and more like there isn't, then it's not actually worrying me at this point although that may quickly change when I see the wiring books and read the factory security troubleshooting notes for the 96 model year SC400.

Hopefully I'm not just being over-confident...