Originally Posted by j9fd3s

my theory is that its the speed limit fuel cut, the JDM ECU's cut the rear rotor at @120kph (or something), and i think when you just throw the ecu into a US car, it thinks you're going too fast.

chipped ecus, which have the limiter removed, do not seem to have this problem and work fine.

Originally Posted by Dak

This may have been covered previously and I didn't search enough( sorry if this is the case) but here goes. So I'd like to do a TII swap eventually. I see complete engines, trans, harness and ecu on ebay all the time. Already knew to not bother with the JDM harness and the motor was prob. only good as a core for rebuilding. What I just discovered last night is the N374ecu doesn't work in a swap most of the time unless you get lucky and get a chipped one, but it does work in USDM factory turbo cars. Most threads on here seem to only talk about/speculate/try to figure out the differences between the N370 and N374 ecu. My thought was what is different in the USDM n/a and turbo cars that would cause the N374 to malfunction. After looking at the ECU pinouts in my FSM here is what I've came up with. If you used your n/a harnes and connected everything in the engine bay correctly why won't it work? I think the problem could lie elsewhere in the car. I've found two pinout differences that aren't in the engine bay. I'll start with the one that's less likely the issue.

Pin 3N on the n/a is an output to the EC-AT control unit. It's not used on the TII.

Now the one that has me curious:
Pin 1U on the n/a is an input connected to the AT switch. It's signal to the ecu is:
A/T Trans = approx. 0V
M/T Trans = approx. 12V

Pin 1U on the turbo is an input from Mileage sensor #2(there is only one on the n/a). It's signal is:

Under 600mi. = approx. 12V
Over 600mi = approx. 0V

Since most swaps are mt cars there will be 12V on this pin. Could it be on the N374 this pin expects 0V but sees 12V and this puts the ecu in some mode that doesn't fire the rear injectors? I read in my searches that there is a speed limiter on the JDM cars. Could this pin be the one used for that? Your trying to start the car but it thinks your going 155kph and shuts fuel and/or spark however they do it. It would make sense if a chipped N374 removes the limiter it may ignore this pin.

Anybody explored this avenue? If it's been tried sorry for the long wasted post. If not it doesn't seem that hard to test. One way since I suspect these sensors live in the instrument cluster( I know the mileage sensors do) would be to swap a TII cluster into a swapped car that has a non working N374. One could also cut the wire to Pin 1U and ground it thus putting it at 0V.

I thought surely someone else has thought of this but if not, maybe I'm onto something.

Originally Posted by RotaryEvolution

nope, i have also experienced the N374 first hand as well running on just the front rotor.

if you simplify the harness and eliminate all the uneeded wires you are probably inadvertantly defeating the problem area. but no one has spent time to find out which circuit is the problematic one, the wiring diagram is in japanese.