zukikat

Thanks dude!

UPDATE

4-21-2011

A couple more very minor 93/96 wiring pin-out discrepancies discovered today...

This increases the current wire mod count from 4 to 6 individual wires total that have required changes so far for this swap to work, otherwise pretty much plug-n-play. That count may go up again once the car is moving on its' own but if the count does increase, of course I'll post the details...

Now that it runs, I've continued troubleshooting other theoretically unrelated issues with this car, like an EXPLODED AND MELTED Parking Lights power feed diode in the driver kick-panel fuseblock caused by a deliberate circuit overload by the same prior owner (2 owners ago) who had also sprayed and blew up the original engiine, among other stupidity. I can't believe it didn't blow the TAIL fuse at some point which still works just fine (tail lights work) although it probably did and it might have an oversized fuse by now, I haven't checked the size of that fuse yet. He also put larger fuses in the headlight circuits, among other dumb moves when it comes to electrical common sense...
The mangled diode socket's pins actually came out of the housing, totally fused/welded to the pins of the diode, when I tried to remove the remaining chunk of the diode from the charred glob of plastic in that area of the fuseblock that used to be the diode's socket so we have no parking lights until I pull the whole fuse block out of the car and see how melted the harness wires are behind it and fab up something safe in its' place to install a new factory diode into... A bigger fuse is always the right solution when they blow, right????? Duh.....


So I got a minor 93/96 suprise while staring at the wiring books in an attempt to follow the signal path and figure out why the AIRBAG light is always on, foolishly assuming that the SRS ECU must actually be unhappy about something either due to a 93/96 wiring discrepancy or more foolish things done by that prior owner...

Turns out that it's another 93/96 issue where the pin in a connector in the passenger kick panel for the "combination meter" AIRBAG warning light got moved to a totally different pin number in the paired adjacent connector and vice versa so as a result the always powered (unswitched) AIRBAG warning light is now getting fed by the OIL LEVEL/TEMP switch and the OIL LEVEL warning light which only gets power when the key is on is getting fed by the SRS ECU, DOH!!!

Once I discovered that issue I sat down with both books and went pin for pin in both connectors for both years and verified that all other pin-outs between those two connectors match up for both years' plugs for all the features this car has and any other unnecessary changes on either year go to empty plug or socket pins in the mated connector so there's nothing else to worry about when it comes to that.

IIRC, connector IK1 Pin 23 in a 93 got moved to connector IK2 pin 10 in a 96 and vice versa for some crazy reason... Fortunately the two connectors are either side by side or one above the other in the same kick panel connector block and it doesn't actually effect the vehicle's operation so it's not a big deal, it's just wierd... I haven't actually gotten into the car to verify this yet but I've triple-checked the two wiring books and that's what I'm expecting to find whenever I dig into that connector block to fix this little "AIRBAG light always on" problem in this car.

I also verified connector IJ2 in both years since IJ1 was the one with the EFI and Ignition B+ power circuit changes to it that started this whole process and got the car to actually start and run once corrected, and those four connectors (IJ1/IJ2, IK1/IK2) are all in the engine harness loom coming into the car. There is another connector or two that appear to be for the a/c system and possibly the hydro-fan ECU that also come from the engine harness and I'll be checking them once I verify which connector numbers they are. The two TRAC ECU connectors and THIRD ABS ECU connector that does NOT apply to an "ABS W/O-TRAC" car also come from the engine harness but I'm ignoring them because this car doesn't have TRAC.

There's also a possibility that the two rear ABS speed sensors' wiring (4 pins total) might need some alteration but I won't know that until we actually get the remaining inherited unfinished mechanical portions of this swap done and get the car moving on its' own again so I can delve a little deeper into that if it proves to be necessary.
There are also some minor TRAC wiring and TRAC related ABS wiring discrepancies between the two model years' systems but since this car didn't come with TRAC at all originally and I have no intention of adding the trac pump and such to it I'm hoping that the lack of TRAC fuses and relays will automatically make that a non-issue for us, but we'll see...

MrSatoV

Zukikat, you're awesome dude. This is a NASTY project you've taken on, and it isn't even your car. Not only do you have strong resolve, keen troubleshooting skills, intelligence, and whatever else necessary to actually pull this off, but you're an amazing friend too.

I'm sure there will be people coming to this forum at some point who will thank God you did this and wrote about it. I found it because I'm trying to figure out how I can read the OBD-I codes on my 92 SC400 because I have an engine light on. There's some other weird things going on too, and I have software that can do all sorts of things/diagnostics, but thats for OBD-II. My problem might just be solved with an OBD1 to OBD2 adapter... makes me feel guilty after reading what you're going through! LOL

Cheers!

zukikat

No need to make any diagnostic adapters or feel guilty at all.
You do NOT need any sort of adapter for your OBD-I car and there's no real point in trying to make one because the car isn't going to create any OBD-II signals and the reader won't know what to do with your car's OBD-I signals either.

Plus your car is basically capable of telling you every diagnostic issue it knows about, whatever made the check engine light come on, without any type of code reader at all.
If you have a piece of wire or even a paperclip you have everything you need to read your car's trouble codes. I don't like using a paperclip because it screws up the pins inside the diagnostic connectors and stranded wire doesn't but that's up to you.

To investigate a check engine light problem on any Toyota/Lexus OBD-I vehicle all the way back to about 1986/87 is actually very simple.
On your 1992 SC400 There's a long skinny capped black rectangular "diagnostic" connector under the hood on the left front area of the engine itself iirc and a sort of round-ish grey one hidden waaaay down on the lower dash near the hood release lever with a hinged cover that swings open and is labelled inside it. You can use either of them since they both have the necessary pins in them for this task.
I prefer dealing with the one in the engine bay because it's easier to see and much harder for the test jumper to fall out of but there's a terminal in both of those connectors labelled E1 and another labelled TE1 although the pin layouts of the two connectors are VERY different so read their very well labelled lids carefully and be 100% certain you're on the right pins at all times because you can screw things up by connecting incorrect terminals together!!!

In the engine bay diagnostic connector it's the center pin of the 3x3 terminal section and one of the corner pins of that same section as labelled in the cap.

Just take a short piece of wire, strip the two ends, insert one end into the E1 terminal and the other into the TE1 terminal as labelled inside the connector cap, then get in the car and turn the key to ON without starting the car and watch the flashing patterns of the check engine light to read any 2-digit trouble codes it has stored. You can also turn the key on and then insert the jumper. If you insert the jumper and can't get the light to flash when the key has been turned on, try the other diagnostic connector.

All OBD-I diagnostic trouble codes are 2-digits so this is the way to read the codes by the flashes of the check engine light.
Once the jumper is properly inserted and the key is on without the engine running, the check engine light will flash kinda medium paced a few times for the first digit, then a slightly longer pause, then it'll do that original pace again for the second of the 2-digits for the first stored trouble code followed by a much longer pause.
Then if there are more codes stored it'll flash the first and second digit of the next code the same way followed by another long pause, and so on and so on depending on how many trouble codes are stored. Don't worry if you miss a digit because once it's gone through and flashed all the codes it's got stored it'll do 'em all over again for however long the test jumper is inserted and the key is on. I'd recommend having something to write them down on handy and counting them through the whole cycle at least two or three times to make absolutely sure you've got all of 'em and that you've got 'em all correct before you go try to look them up and see what they mean...

If there are no stored codes at all and it thinks all is well it'll just flash a rapid constant on/off/on/off over and over with no long pauses at all.

NOTE!!!
Disconnecting the battery for more than a few seconds or letting the battery go dead at any point will clear out any codes that were stored so the car must have been driven and been acting up and then checked for codes to give you a proper diagnostic trouble codes list for the problem(s) that it thinks it's having.

The Overdrive OFF light will also flash and other warning lights too, I forget which ones in the SC, and if all is okay with any of those systems independently then they'll independently do the rapid flash to say so. If any of them are having issues they'll also flash their warning light in the same 1st then 2nd digit pattern of any codes they have stored as well.

There's probably a list of what the codes mean on this site somewhere, although you can probably also google them too.

There's another pair of terminals in the dashboard's diagnostic connector that will flash any stored trouble codes in systems like the AIRBAG and ABS and TRAC as well but I forget which terminals they are. Instructions with the labels for those terminals can be found in the "how to reset the airbag warning light" instructions on a sc/soarer website that's called something like "intelexual.net" or something like that (check in google) but that info is probably available on here too.

There's also a "test driving" process for the OBD-I cars involving a jumper being inserted into certain other terminals and left inserted while driving the car which I actually want to do on my 94 LS400 but I haven't checked into that yet to find out which pins and how to read whatever info it might provide in real-time during and post test drive and I'm not sure how informative that process really is overall compared to just reading the stored trouble codes and following the manual for what things they suggest to check...

Hope that helps!

Thanks for the kind words!
It actually wasn't a big deal overall to get the car to run on the newer ECU and all.
Basically the addition of an OBD-II diagnostic connector to go with the OBD-II ECU and matching "engine harness", and a total of 5 actual wire changes within that harness seems to have done the trick and converted it to work in the OBD-I car.
We've only driven the car three times so far since I'm concerned about the unknown timing belt history but other than a misbehaving speedo (odometer and cruise control both work though!) it seems that the car's behaving properly in both city traffic and the few 5-10 mile freeway runs we did in it the other night.
I'm still unsure about the rear ABS sensors' wiring being proper or not for the newer engine harness connections due to the TRAC engine in the non-TRAC chassis but the brakes seem to work fine and I haven't had a chance to investigate or test the ABS yet so we'll see how it goes once the timing belt job is done, hopefully within the next few weeks...

CACressida

iTrader: (1)

I dropped a 97 LS400 1UZ OBDII engine in my OBDI Cressida and all I did was wire the fuel pump to come on with ignition power and supply power to the injectors and ignitors with the same wire. So far no problems other than the minor Immobilizer issue I ran into which I fixed with a 95 ECU. BTW, Toyota thought it would be nice to swap the ignitor wires on the Immobilized computers to run 180 off so the engine would back fire for the very purpose of swapping a non immobilized computer in an immobilized car.

I'm guessing the TRAC on the 1UZ just cut's power when wheel spin is detected unlike the TRAC in my VVTi 1UZ which uses a combination of throttle and brakes to control wheel spin more effectively via the ABS. Why not just get rid of TRAC on your SC since TRAC on the early cars was junk.

zukikat

Thanks for the feedback!
I'm sure someone will find the igniter immobilizer wire swap thing helpful at some point but I was lucky enough not to have to deal with it on the 96 engine and 96 ECU.

The older/original Toyota/Lexus TRAC system has a second "butterfly" in the throttle body on the intake side (prior to the one that's connected to the accelerator pedal) which the ECU uses to manipulate power when it detects inconsistent wheel spin between the two rear tires and it also interacts with the ABS and has a unit called a "Trac pump" on some model years as well which I "think" it uses to apply the brakes if it wants to but it's been years since I researched that system at all.
There were changes made to the TRAC system at some point along the way which I "think" eliminated the TRAC pump but I'm not sure which year they revised it from the original version. I know that by 1998 my Twin-Turbo Supra's TRAC system didn't have a trac pump and the TRAC ECU connectors were very different from the OBD-I years' TRAC system that my 1993 Twin-Turbo Supra had (which looks like what the SC and LS also got) but I didn't really study it at all so I don't know the specifics.

This car that the newer year of engine was dropped into didn't have TRAC even though the engine has all the engine based TRAC components and its' harness has the appropriate TRAC connectors everywhere but since the chassis does not have the chassis-side TRAC components to support that system I've just left the 2 TRAC ECU connectors and the 3rd ABS connector for the TRAC compatible ABS computer in the interior passenger dash area all unplugged. The original non-TRAC ABS computer the car got from the factory only has 2 connectors and they're totally different sizes from the TRAC ABS computer which makes ABS connector number 3 useless anyway...

We haven't really driven the car hard enough yet to see if the newer main ECU cares that the TRAC ECU is unplugged or if the ABS has any issues with the different engine harness in the older chassis yet. It's now pretty much in a holding pattern awaiting a timing belt job because the 96 1UZ is an interference engine and we have no idea how many miles are on the belt and it sat up for over 4 years that we know of and he's intending to commute about 90 miles a day every weekday with this car.
It starts right up and idles normally and we've made in-town trips to get lunch in it a few times and been on the freeway for a few miles a couple of times already so for now he's satisfied with my progress. Once he orders the parts and we do the timing belt and water pump replacement we'll see how the car does for his work commute after that.