2jzBrandon

I bought my 93 SC300 on facebook marketplace it came with the wrong ecu he had put a 97 ECU in a 93 shaking my head currently. Im wondering if that could have damaged any wiring since im guessing some of the wires route to different places on the 97. The car still started and everything functioned right when I bought it the idle was actually decent which suprised me. I wasnt able to scan it so I looked at the ecu and sure enough it was the part number for a 97. Just wondering if anything could have been possibly damaged from that ecu being hooked up? Before buying the right ECU

Arsenii

Hello,

What exactly is the issue with your car currently?

While those ECUs could be incompatible, I doubt that any damage that could be done would be spread out over some time, even if there is something that could cause damage, that damage will happen immediately. Older Lexus models suffered heavily from the ECU failures, the tricky times of new technologies, could be that the previous owner actually saved you trouble instead of creating them. That said, without knowing what exactly is the issue you have currently, it's hard to tell anything..

Hope this helps and best of luck!

KahnBB6

iTrader: (5)

The only major things that a much newer 1997 OBD2 ECU installed into your 1993 SC300 would affect are your oxygen sensors (which are simpler non-heated two-wire front O2's on the cast iron manifold vs the OBD2 4-wire heated O2 sensors) and whether or not your 1993 has original CA emissions wiring which would mean that it came earlier than federal cars with a 3rd O2 sensor (heated 4-wire) on the 2nd catalytic convertor.

1997 SC300 ECU's still operate the older style distributor ignition system so that would be unaffected between '93 and '97. Same with the EGR system being identical from 1992-1997.

That being said you do need a 1992-1994 SC300 ECU with the matching transmission and emission type installed instead of the 1997 ECU. The 97 ECU is not getting the signals it is expecting from the early style two wire non-heated front O2 sensors and is probably making the engine run rich in order to compensate. Eventually this rich running condition will foul your catalytic convertors.

I don't think the engine itself would encounter any damage as a result but it's not going to be running perfectly with a newer OBD2 computer installed into an OBD1 chassis that has no wiring modifications to appropriately run an OBD2 ECU.

2jzBrandon

Thanks that explains alot. It would burn my eyes while it was running. Im guessing my cats are probably screwed because the idot probably ran it like that for a long time.

1997Soarer

iTrader: (1)

KahnBB6 is right. I don't think you're looking at any electronic damage to the car. Honestly any damage would likely end up being done to the ECU, since it was getting voltages its not used to seeing.
The OBD2 ecus read different signal parameters for the O2 sensors and MAF, and also look for more things (rear O2s, crank sensor, and I think another knock sensor). That ecu probably ran like crap in OBD2 limp mode and that explains why you were smelling gas.
I'm actually surprised the car ran well enough to drive. This is the first time I have heard of a newer computer in an older car.
Don't get too hard on yourself, the cats were likely already bad. The guy probably swapped ecus because the older one kept failing.


Just in case, google a 92 SC engine bay and compare it to pics of the 97 SC engine bay. Make sure your MAFs match the year.

KahnBB6

iTrader: (5)

^^ Thank you for also binging up the MAFs. I completely forgot to mention that in my post.

Yes, the 1992-1995 SC300 (and SC400) use a Karman Vortex (KV) style MAF. You should never, ever, ever, ever, ever, EVER clean those. They employ an internal mirror used to read light in some way that determines the air density.

If you introduce any type of solvent in there (or if the previous owner did) it can permanently damage the sensor portion. If such damage has occurred, go onto ebay and try to find a known good working used OEM 1992-1994 SC300/400 MAF sensor. You don't need the whole housing-- just the sensor. However some sellers include the whole aluminum housing and the sensor.

1996 and up SC300's and SC400's used a different type of MAF sensor which in some model years *may* be similar to or the same as the MAF sensor used in Supra MKIV NA's from 1993+... but I've never fully looked into that and so cannot say.

For your purposes OP, focus on the 1992-1994 KV type MAF that your car originally came with.

Also I just remembered: 1996+ SC300's have a crank position sensor mounted off the oil pump which that 1997 ECU is looking for. Pre-1996 2JZ-GE engines do not have the crank position sensor and their ECU's rely on the internal cam position sensor built into the distributor.

...

As for the cats... see how they're doing once you've got the correct engine control ECU in there. The previous owner probably did foul them but maybe with even one of them you'll do okay for a bit longer.

Catco has historically made the most bolt-in friendly aftermarket replacement cats. The front unit is a bit difficult. They do have a number where you can contact them and request they build you a direct fit but it may require sending in a template (ie: your old shot OEM cats) in order for the to get it just right. I haven't checked into that since 2016 so I hope they still offer the service.

2jzBrandon

I just ordered the right ecu, and hopefully everything goes well. If it runs like **** after the ecu, at least I'll be able to run the codes and see exactly what's going on. Ill probably just put headers on it if my cats are fouled. I mean, its my first car, and I want to have some fun with it. Thanks for all the explanations; they made me a little less worried about the thing.

EDIT: I found out the issue I put the right ecu in the car now it scans and runs amazing at first it wouldnt start but then I bypassed the fuel pump ecu and now it works im not sure why this fuel pump ecu worked on my 97 ecu and not the right ecu things so goofy.