I've got a full S5 long block JDM swap on the way from Japan2LA and I've been reading up on the swap process and I'm a little confused about the wiring harness/ECU issue.

My question is, can I use the JDM harness and jspec ECU since everything that the wiring harness will connect to will be JDM? Everything that controls the engine goes to the ECU from the engine harness, so I don't see why you couldn't. This is assuming that the pinouts for the other things, like gauge cluster and idiot lights are the same.

Does any body have a pinout for the N374?

 

are you swapping between series?

 

Nope. 1990 GXL.

 

isnt the s5 able to do a pin swap and use the na harness with the turbo 2 components?

 

oh well then. short answer is yes you can use a jdm harness. you will just have to obviously make the wires longer but other than that its just a straight plug an play type deal

 

The JDM harness is for a RHD so it is designed to exit the opposite side of the car than USDM. The plugs on the engine side won't be the right length to reach. I don't have any direct experience, just educated guess and a little research, I have a JDM 13B.

I wouldn't rely on the N374 ECU, do a little research and you'll find alot of people having trouble getting the fuel injectors to work. Going by memory the rear injectors are the problem. There is a mystery black box tied to N374 ECUs...literally connected to them. There is alot of debate what that box does, but I never researched enough to learn if anyone has figured out the whats and whys.

If I were you I'd get an N370 ECU and either research the pins that need swapped from your N/A harness to operate the turbo ECU or also buy an N370 harness. I can dig up the information I have on pin swapping, though the info may not be as accurate as some of the more experienced members.

 

The jdm harness will not work without some serious modification . Its easier to use a n/a harness or a-spec harness. Less headache for the newbies.
Thanks Robert

 

Meh. Not the answer I wanted. I was hoping to avoid having to take off the UIM to get the injector clips connected. I was also hoping to be able to use the 374 instead of buying a 370.

So, anybody got an N370 for sale?

 

Hehe, taking the UIM off will seem like nothing compared to other work needed. Well if it's a swap from N/A to turbo that is. If it's N/A your going to have to decide about driveshafts and differentials. Full swap would have you getting a turbo differential and driveshaft. Or mazdatrix sells a driveshaft that will let you use the turbo tranny with an N/A differential.

 

Yeah, I got the whole package: long block, tranny, ds, diff, halfshafts.

It's mostly the wiring harness and ECU that are giving me fits.

 

NA EM harness > US TII EM harness > Hacked up/extended Jspec EM harness. There is nothing plug and play about using any TII EM harness.

 

Can you point me to a resource about this? I keep hearing people saying this, but I've not heard of anyone trying it.

It also seems that the issues with the rear rotor not firing are from people doing a mix/match swap. Not a complete changeout like I'm going to.

Can anybody for sure say that they've tried a full NA S5 to TII S5 swap using the N374 and had the rear rotor issue which was resolved by getting the N370?

 

EM = engine management?

I hear you, what I'm wondering is why? What specifically is the problem (aside from length) of using the N374, Jspec EM harness and the Jspec long block. I sure seems like it should work. I'm not saying it should, I would just like to know it doesn't.

 

The reason you aren't finding info about pinouts for N374 ECU and JDM harnesses might be that most people found it easier to use the USDM ECU and harnesses rather than put work into making a RHD harness works in a LHD car. Same reason might be true on researching pinouts for N374 ECU compared to N370 ECU.

But I'm just guessing and very well might be talking out of my ***??

 

EM = EMissions harness, which is what Mazda calls it in the manual.

To use any TII EM harness with an NA front (F) harness (runs all over the car), you have to repin two separate plug junctions. They can't just be plugged together because turbo and N/A cars have the wires in different locations on the plugs. I believe on S5s as well as S4s, you have to run new wires to the back of the alternator since they're incorporated into different harnesses on NAs and TIIs. Jspec TII EM harnesses are also too short for LHD cars, which would mean extending every single wire, and they also do not have the wiper motor wiring in the harness.

N374 and N370 have the same pinouts (except one emissions pin I think), but the N374 has a history of not working properly when used with US-spec harnesses. Or at least it does in swapped cars. Apparently it usually works if placed in S5 TIIs. Go figure.

 

For S5 to use the N/A harness the only things that would have to be repinned are the knock sensor and the factory boost controller (on the rats nest). If you do emissions removal and have aftermarket exhaust, the boost controller will be gone. I've heard both not to bother with the knock sensor and also to do it, most people say it's useless on these cars anyway, thats up to you, it's only 1 wire. You could do the S5 TII harness which I believe doesn't require any of the modifications that the S4 harness does, but I'm not certain as I did the N/A. Don't even bother with the JSPEC harness. You should be pulling the motor apart to put new gaskets on it anyway.

As for the n374, give it a try before you go looking for an n370. Some people have them work and some don't, might as well give it a shot since you already have it.

 

There is tons of info on the board. Just search for t2 swap. I have done tons of swaps, So i have lots of experence with that. I have also done both turbo vert for hozzmanrx7.
Thanks Robert

 

All right, I'm going to do something that I normally don't, and take this advice to rewire my NA harness and put it on. I suppose this gives me the opportunity to replace a few gaskets and change out the OMP lines as well.

Thanks all for the help!!!