ECU compatibility
11-20-13, 05:30 PM
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ECU compatibility
I have come across a 93 sc400 ecu. I know it isn't 100% compatible with my 95 but will it just light up my check engine light or can I do some serious damage?
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11-21-13, 08:06 PM
#8
Here are the changes Lexus made from 1992 to 1995. Post #4. Not entirely sure why they aren't interchangeable, all I know is that they wont fit.
https://www.clublexus.com/forums/sc-...fferences.html
https://www.clublexus.com/forums/sc-...fferences.html
11-22-13, 10:38 AM
#9
go to page 40 and 41 and read what is new and what isn't new in 1995.
http://www.mr2.com/files/mr2/techinf...e95LS1uz-1.pdf
basically the reason they won't work is in 92-94 the 1uzfe uses batch fire injection where it fires pairs of injectors together, and in 1995 they went to true sequential injections where it is only fired right before its needed.
if you hook up a 95 ecu to a 92-94 harness, you will probably get double the injection and flood the motor.
If you hook up a 92-94 ecu to a 95 in your case, you would probably only get half the fuel on half the cylinders, the other half of the cylinders receiving no fuel which is not gonna cut it.
you could rewire the outputs to the injectors at the ecu by pairing off the injector triggers to emulate the older harness and use an older ecu, but you would be reverting to batch fire injection, loosing the better tune on the newer ecu's and their other features. also could be other issues.
also 1995+ the 1uz became a possible interference motor due to the slight bump in compression just for your info.
So you could use an older ecu, but it would require an older harness and changing the harness on one is a lot of work, or you would have to modify your harness at the ecu at the least. you cannot use a 96 ecu because they switched to odb2, so if you wanted to make that 96 switch you would have to do some wiring cause it uses a newer kind of maf sensor etc.. it can be done though but its easier to buy a 95 ecu in your case.
http://www.mr2.com/files/mr2/techinf...e95LS1uz-1.pdf
basically the reason they won't work is in 92-94 the 1uzfe uses batch fire injection where it fires pairs of injectors together, and in 1995 they went to true sequential injections where it is only fired right before its needed.
if you hook up a 95 ecu to a 92-94 harness, you will probably get double the injection and flood the motor.
If you hook up a 92-94 ecu to a 95 in your case, you would probably only get half the fuel on half the cylinders, the other half of the cylinders receiving no fuel which is not gonna cut it.
you could rewire the outputs to the injectors at the ecu by pairing off the injector triggers to emulate the older harness and use an older ecu, but you would be reverting to batch fire injection, loosing the better tune on the newer ecu's and their other features. also could be other issues.
also 1995+ the 1uz became a possible interference motor due to the slight bump in compression just for your info.
So you could use an older ecu, but it would require an older harness and changing the harness on one is a lot of work, or you would have to modify your harness at the ecu at the least. you cannot use a 96 ecu because they switched to odb2, so if you wanted to make that 96 switch you would have to do some wiring cause it uses a newer kind of maf sensor etc.. it can be done though but its easier to buy a 95 ecu in your case.
Last edited by Ali SC3; 11-22-13 at 10:43 AM.
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