Well, I searched the forum but haven't found much on this so figured I'd ask the experts.

I'm currently in the midst of reinstalling the large front ring harness and engine harness on my '93 CA model FD. Bought an engine harness/ECU recently off a fellow forum member which apparently came from a '93 as well, but I have noticed a few things when comparing my old (fried) harness to the good harness.

The new harness is missing the yellow solenoid connector for the EGR. No wires were cut, etc. it was just never there. I suspect this is either a 95 harness or possibly non-CA setup. Didn't they get rid of the EGR in 95?

can anyone identify the ECU/harness by these part numbers:

N3A7-18-05ZG -- harness
N3A3-18-881A -- ECU

Now, I don't mind ditching my EGR but I do have to pass CA smog. Will this still be possible? I've noticed a few of the other connector are slightly different and some wires are different in the plugs, but I am still going through them one by one. Figured if someone could identify these from the above parts numbers that would make things quick & easy.

Any help would be greatly appreciated.

thanks,
Mike

 

Alright I've spent a little more time going through each connector on both harnesses and found 3 more connectors that the good one doesn't have. 2 go the the ACV on the side of the lower intake manifold, 1 goes to the idle air control valve which is attached to the underside of the upper intake manifold. The last of course goes to the EGR solenoid in the rats nest.

These are the connectors in question (with yellow zip ties around them) on my fried harness:



This is the good harness:



Also snapped a shot of the ACV plugs and the other one under the upper manifold.

So which is it, a non-CA model harness or 95 harness? I know it has to be one or the other. Really curious which it is. I tried googling the above part #s but it wasn't much help.

Mike

 

the did...but the harness didn't change.

and no. They will test your EGR valve...and your car must stall. At least that's what I'm told.

you will need the ACV to pass emissions and have a proper idling car with the stock ECU. You will also need to have the ISC to have a proper idling/functioning car...

 

Hmm, that's what I thought. What do non-CA models have in place of the ACV and ISC, just block off plates? Heck I'd convert mine to "non-CA" if it was that easy but for some reason I doubt it is.

Mike

 

i doubt most shops will test the EGR valve since it is a total bitch to get to on the FD but even if they do it will still act normally since all they do here is a manual test of the valve to be sure it is working, checking the solenoid would be impossible unless they charged $400 to do a smog.

without the ISC the car can still idle but it may be a little more of a pain to keep it from stalling when electrical/mechanical loads are turned on.

no idea on the differences between the ACVs, never seen one with only a single plug and i have dealt with out of state emissions cars before.

 

Here is a list of emissions harness part numbers for 1993 + 1995 domestic models listed in the FPMs.
I don't have 1994 models, but expect all but the last letter of each number to be the same.

1993
MT n3a1-18-052e
AT n3a2-18-052b

1994 ?

1995
MT n3a1-18-052f
MT n3a1-18-052g
AT n3a2-18-052h
AT n3a2-18-052j

Unless calif part numbers weren't listed in the Mazda FPM, could N3A7 series harnesses possibly be for UK or Europe or Australia or... ? and/or newer than 1995 ?
Why not join Mazda USA's website and ask them ?
They might have access to worldwide part numbers if you can't source the PN domestically.

Good luck with it.

 

you said you also bought the ECU with the harness. Does the ECU come with the mounting bracket? If so, it it set up for mouting on the left side or for the right side? It might tell you if you have a domestic setup or a JDM setup.

 

A quick google search suggests that N3A7 is the ECU that came in the 1992-1994 Japanese RX-7's. I'd bet that you've got a JDM harness also, which would explain some of the missing emissions equipment.


http://www.kaele.com/~kashima/car/rx7.html
http://translate.google.com/translat...ial%26hs%3D4F9
https://www.rx7club.com/showpost.php...7&postcount=10


-s-

 

N3A7 is the harness prefix though, not the ECU. I sure hope this isn't a JDM setup. That's highly unlikely as the guy I bought it from is maybe 2-3 hrs. away from me in California.

I snapped a pic of the "new" ECU next to my old fried one. Bad one is on the left, yes I know it says 94 RX7 on it -- previous owner tried another ECU I believe in hopes of fixing the original problem. They are identical other than the last digit in the part #. A for the 93 ECU and B for the 94 ECU. Mounting brackets are both the same.



I'm pretty sure this is just a federal (non-CA) setup, but I want to confirm before I try to actually use it. I am also wondering what the federal cars have in place of the EGR valve, and how if at all the ACV and idle air control valves are different. Anyone with a non-CA car have photos of these areas?

thanks,
Mike

 

Can tell you the Japanese cars (and I'd hazard a guess, the entire production run) came with the air and idle speed valves.

The plugs for the ACV in your first picture look identical to the 92 JDM car's - which I believe are the basis for your 93's. I've got no memory of what the idle connector looked like.

The N3A7 prefix means manual, whereas N3A8 is auto.

Daioni sent me this info a while back (for V I cars??), appears to be wholesale changes and superceding depending on chassis number early on - and the list looks a bit cropped, so possibly others as well.



The highlighted harness is non-EGR.

 

The idle air control valve is the one with the orange center with a yellow zip tie on it.

thanks for that list.

I originally started out thinking this might work out, but today I found another plug that is different. It's the blue connector right next to the 2 yellow ones that plug into the ECU. On my harness it has 10 pins, on the new one 12 pins. It physically won't plug in to the other smaller harness that goes behind the glovebox. The new one also has 1 extra wire, a white w/blue stripe that's not on my old harness. I'm sure it's possible to get working with a bunch of rewiring and swapping of plugs around, but I'm not sure I want to go through all that hassle.

damn CA smog.

Mike

 

Well, I've done a bit more research and actually found some old info on the forum regarding the ECUs:

'93
N3A1 - Fed MT
N3A2 - Fed AT
N3A3 (ends in 881A) - Cali MT
N3A4 (ends in 881A) - Cali AT

'94
N3C1 - Fed MT
N3C2 - Fed AT
N3A3 (ends in 881B) - Cali MT
N3A4 (ends in 881C) - Cali MT

'95
N3D8 - Fed MT
N3D9 - Fed AT
N3E1 - Cali MT
N3E2 - Cali AT

Soo, it appears I do have both California ECUs. Now I'm even more confused though, because I have no idea why the harness the good ECU came with is missing 4 connectors. Still trying to research that harness part #.

Maybe I'm missing something, but to me it seems logical that if I used this ECU/harness combo there are going to be error codes due to the missing EGR solenoid connector.. or is it the other EGR connector that generates the error code?

Mike

 

Today I went through every wire on the 2 yellow (EM) plugs that go into the ECU, found several differences. On the smaller of the 2 (16 pins total), pin 3K isn't present on the good harness. I looked this up in the 94 wiring diagram, and it goes to the "relief 2 solenoid valve." Not exactly sure what that does, but I believe it's related to one of the missing connectors for the ACV.

On the larger of the 2 connectors (26 pins total), pin 4P and 4F aren't present on the good harness. 4F deals with the split air bypass solenoid valve and 4P is the AWS solenoid valve. Also pins 4O and 4E are different colors when compared to my old harness. 4O deals with the EGR solenoid valve and 4E is the crankshaft position sensor.

So judging by these differences, anyone have any ideas as to what this harness is from?

I will try emailing Mazda about this part #, as it seems I keep hitting dead ends on what year/model it is from.

thanks,
Mike

 

I'm not aware of any wiring harness differences in the US models (at least between a CA and non-CA cars). Sounds like someone probably modded the one you have to remove what they weren't using, or I suppose its possible to be a Japan model based harness as I don't believe their models came with the EGR or ACV. However, I'm a USA guy so who knows!

 

Yeah that's what is so strange, the harness does not appear to have been modified at all. It looks factory to me.

Mike

 

Emailed Ray about this harness dilemma earlier today, he got right back to me about it. The man is amazing!

Basically, he said the correct harness # should be N3A1-18-05ZG and he doesn't know what the N3A7 prefix is. The only harness #s for the US FDs are N3A1 & N3A2 (manual/auto I presume).

Apparently this IS after all a Japan (or some other country) spec. harness, yet it was mated to a CA ECU. I can't really say why, as this didn't come out of my car. Very weird.

Just so everyone doesn't think I'm crazy (or can't read), I snapped a couple harness shots of the part # and the blue connector difference when compared to my old harness.



Mike

 

See you worked it out, checked out a spare harness I have for a version II or III engine (dark intake elbow) and surprise, surprise N3A7-18-05ZG came up on the tag.

It definately has connectors for both ACV and IAC, so something strange going on with yours.

Here's the ECU end



and for anyone who doubts they had ACV's.



It will plug into ECU N3A7 18 881C, not entirely sure what year that is, I suspect 92 though.