Has anyone successfully used the n374 ecu on a s5 na to t2 swap while using the na cars wiring harnesses?

I was working on a turbo swap in a s5 na car and ran into ecu issues.
I tried to use the n374 ecu and it ended up doing the typical run verrrrry poorly on 1 rotor.
Swapping the na n350 ecu in and the car fired right up and idled and reved freely.
this is using na wiring harnesses


after searching around the general consensus is that the jspec ecu seems to work fine in real s5 turbos but something with the NA underdash harness causes the jspec ecu to run bad. Some say chipping the ecu fixes this issue too. But id rather like to avoid chipping if possible. Further I cant seem to locate a real usdm ecu at the moment either...

Has anyone figured out what wiring differences are causing this and or how to fix it?
some have speculated it has to do with the Japanese speed limiter, but without a translated Japanese wiring diagram it is pretty hard to tell whats what.

 

Check out eBay there are usually some S5 T2 harnesses and ECUs for sale there, I sold a JDM ECU not long ago and the new owner said he had no problems using it since but I believe he has a factory T2 not a swap

 

Rtek7 ECU Upgrade Detailed Information

you can send an N374 in and they will know how to make it work

 

yes, i hate to say search n00b, but i don't recall which wire is different, i think 1F? searching will reveal a lengthy thread where me and Satch, and Gregs22 figured it out.

the US car has a mileage switch, on the same pin that the JDM car has the speed limiter, so depending on the position of the mileage switch, the JDM ecu will either run fine, or it will run on 1 rotor because you're going too fast.

if you want to look yourself, foxed.ca has the JDM wiring manual, and you can compare.

 

Thanks this is something I suspected, I will dig deeper into this, thanks!

 

Remember "1 merica" for pin 1M? That's what I recall.

 

1m is the mileage sensor ill try this wire and see if the results change

 

I believe you ground that wire and the engine will operate properly. If the mileage on the odometer is between 100k and 120k the wire will output 12 volts to the ECU, but if the mileage is between 120k and 200k then it outputs a ground signal to the ECU. One of these signals causes the ECU to cause the engine to act funky so you have to make the wire to act differently, thus if it is 12 volts then it needs to be grounded and so on.

 

so I cut the 1M wire and left it an open connection and the car starts and seems to run normally, I only drove it around the cudisac in first tho as I had some other stuff to work on to make it road worthy

 

Why not just wire in a relay with both 12v and Ground, with pin 30 going to the ECU, ala power window relay mod? Best of both worlds, and you can put in a "run like ****" anti-theft switch

 

Im just curious what the mileage switch changes on the ecu...

 

It changes one of the emission solenoids. One of these solenoids is activated for the first 20k and not from 20k to 100k but after 100k is hit it activates the solenoid for the next 20 k (100k to 120k). If this wire runs to a pin which is used for another purpose then the ECU is then receiving the wrong signal.

 

That would likely be a good idea.

 

the FSM mentions the thing specifically, its something to do with the split air number 2 i think, anyways its there for some EPA mandated reason, and like you'd expect the old timers had stories of sub 20,000mile cars failing smog, because

 

yes which in this case of the jdm ecu tells the ecu your going 180km/h and results in fuel cut

 

lol most of the time if my car is parked somewhere sketchy I routinely unplug something or remove a fuse or something, so a theif cannot take the car, 95% of thefts of these would be for a joyride or to drive off and steal the rims or something....

 

there are 3-4 different pins between a US T2 and JDM car. the speed limit/mileage switch is the significant one. the US car also has an extra solenoid on the ACV, and the JDM car has a temp sensor in the cat, although not sure if those share a pin.

there is something else too, but really minor