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.

 

here is a thought... retard on shift command??? the auto will be being tested in neutral or in park.. maybe its giving out a detent command along this wire to limit engine power during shift

ie 0V ( potentially ) = no secondary injectors and basic timing


only one way to tell.. bridge it to 12v.. see if secs enable ( disconnect TPS and MAP and free rev engine and observe noid lights )

 

Test condition in the FSM is ignition switch on. I think this is either always at 0V for auto or 12V for manual trans. It lets the n/a ecu know if it is an auto or manual transmission car,but like you say this could be tested. Your test would have to be performed on a car with an auto though, because the manual will already be at 12V on this pin.

 

the JDM cars also have a speed limiter, and its possible that is what we're seeing when the N374 is put into a US car.

this problem is actually odd, i know some of the old school guys used N374's in US t2's without any problems back in the day. they weren't doing T2 swaps though, its T2 into T2.

 

That is what I'm wondering.Is something in the usdm n/a wiring is activating the speed limiter?

I have read of rare cases of unchipped ones working in a swapped car. I wonder if in these cases they had swapped the instrument cluster as well. This should put the same signal to pin 1U as a factory turbo car as both mileage sensors are in the cluster. Does anyone know if when you put a N374 in a US TII if the speed limiter is still active?

 

Maybe those chipped N374 ECU have the speed limiter removed?

 

If someone is running a 370 with a jdm cluster would the speed limiter be active? My friend tried to do an n_a to t2 swap with a 374 ecu and it wouldn't work, tried it with a 370 and it worked, but he's using a jdm cluster and complaining about limits in speed...