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Discussion Starter · #1 ·
Hey guys,
ive been planning on using the uncut 1uz harness from a 92 ls400 untill i saw an artical on lextreme.com written by the guru of 1uz swappage Phil bradshaw that states
"The 90-92 LS400/SC400 ECUs seem to be a problem child for some reason – these have 4 x two-row grey plugs and I have had about a 30% success rate with them so far. They all start and idle ok, but for some reason many won’t rev beyond about 2800 RPM. I do not know hwy this is – it makes no difference whether the loom was cut or intact, whether the auto trans is there or not. I wonder if the missing traction control is part of the problem, but it doesn’t affect any other ECU. "

is this just old info?
is there a cheap, if not free work around to solve this issue?
are any of you running a 90-92 ls400 ecu with a manual trans currently?

Im at the point where i need to decide what ecu to use and the crown ecu he reccomends is impossible to find in the states.... er... impossible or expensive... i forget what one....
 

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you "SHOULD" be able to use a newer ecu.just note that the 95 ecu is different. my roomate with the 1uz swap in his mk3 had this problem. his engine and ecu are unique for that year because of the transition from obd1 to obd2. something about the cold start injector. from what ive been told, dont hold me to it lol.
if its the same plugs, just find a newer ecu. my engine is a 92, and i believe my ecu is a 92, but i have 3 grey plugs, 1 big, 2 smaller. and mine is sc400 components.
 

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Discussion Starter · #3 ·
you "SHOULD" be able to use a newer ecu.just note that the 95 ecu is different. my roomate with the 1uz swap in his mk3 had this problem. his engine and ecu are unique for that year because of the transition from obd1 to obd2. something about the cold start injector. from what ive been told, dont hold me to it lol.
if its the same plugs, just find a newer ecu. my engine is a 92, and i believe my ecu is a 92, but i have 3 grey plugs, 1 big, 2 smaller. and mine is sc400 components.
so your saying use a 93 or 94 ecu?
the plugs on my wire harness that go into the ecu are as you discribed 1 big two smaller all grey. (26, 16, and 22 pin respectively)
 

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well, i just looked at my roomates 95 ecu and my 92, the plugs physically look the same.if indeed the ecu is the culprit of the problem and not something else, yes, the 93 and 94 ecu should work. but, dont put my word before phils lol, he obviously has been doing something right.
 

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Discussion Starter · #5 ·
Got an email back from Phil on the issue....
"Since I wrote that article I have discovered that the problem is actually a designed in feature (go figure) - the solution is to fit /connect/simulate the dash speed sensor. Depending o nthe project, a Mazda MX5/Miata gearbox in line speed sensor provides the required pulses. Just connect the spend sensor to earth.
"
I think this is what hes talking about.... i emailed him the same pic for clarification
 

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i have a 93 ls400 and can tell you the 90-92 ecu's are diff then the 93-94. and if you want to eliminate traction control on a traction control ecu then just jump the vc to the vta2 on the ecu. i have ecu pinouts for both of the first gen ls400 ecu styles if you need them.

as for the rev issue you can have the ecu rebuilt with a lifetime warranty for $100 by ati. they have deals on ebay had mine rebuilt by them just so i know it wont crap out on me as i have to drive 75 miles a day for work.
 

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I've wired up a Celsior ecu before, didn't have any issues.
Just make sure you wire the SPD pin to the dash output (the wire that goes to the cruise control module needs to be wired to the SPD pin).

And be careful with the 93-94 ecu's compared to the 95+ ecu's. From what I've heard the plugs are all the same, but the pinouts are very different, and you can fry the ecu if you use the wrong harness.

Also, with the 90-92 ecu's, the 4th plug is part of the dash loom, not the engine loom, so make sure you get it.
 
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