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Yeah, I'm still working on this. One thing that has struck me over the course of my research on this is that I've come across three threads where the original poster was doing this same thing, asked a lot of questions, and towards the end wrote "I'm almost done, it was hard, but when I finish I'll post everything I did for posterity" <b><i>and then never posted again.</i></b> Three. Three times. So, to make sure I don't make #4, I'll keep this updated until the end.
I've got FSMs, lots of posts, and so forth saved, but the thing I've found most helpful for the "hard stuff" is an extra S5 body harness that I've laid out and unbound, so I can physically trace how the ECU and FEM plug wires are sourced. Needed, because jeez, a lot of the color codes posted for the FEM plugs are way off from the three harnesses (two S5, one S4) I'm looking at. Nevertheless, I'll try to cover my bases with more than just color codes. Double checking, triple checking, because I don't want to get something wrong and have to dig back in, or worse, blow my chipped ECU.
I'll skip the mechanical work because I assume people can figure out how to drop in a motor or they wouldn't even be attempting this. So without further adieu...
First and easiest stuff is the F31 plug. Acquire one from an S5 front harness, leaving yourself plenty of wire. Strip back the wrap from the old S4 one, exposing the wires. Don't cut them all at once, because some of the wires are the same or similar color and oh man, you'll yank your hair out when you realize your mistake. I didn't learn that the hard way, and patted myself on the back for it. Anyway, one wire at a time, cut and splice from the S4 pin to the S5 pin, leaving yourself enough wire. You don't want the plug to come up short when all is said and done and you go to plug in. Some wires from the S4 won't be used because they're relocated to the EM harness and already will go where they're supposed to, like the CAS wires. I'll also type the pinouts rather than post a pic, because don't we all love "this file is no longer available" five years down the road.
Remember, this is looking at the <b>wire side</b>, not the "hole side". It's the view you would have of the ports on the back of the ECU itself. Clip facing <b>up</b>.
1A : 1F
1B : 1F
1C : cut and terminate - <i>Air Bypass Relay, on S5 EM harness</i>
1D : 1D
1E : 1O
1F : 1L
1G : 1R
1H : cut and terminate - <i>Water Temp Switch, not on S5</i>
1I : 1T
1J : 1I
1K : cut and terminate - <i>Shift Indicator Light, not on S5</i>
1L : 1Q
1M : 1V
1N : cut and terminate - <i>Crank Angle Sensor, on S5 EM harness</i>
10 : 1M+1U (if there)
1P : cut and terminate - <i>Crank Angle Sensor, on S5 EM harness</i>
1Q : cut and terminate - <i>Crank Angle Sensor, on S5 EM harness</i>
1R : 1N
1S : cut and terminate - <i>Port Air Solenoid Valve, on S5 EM harness</i>
1T : cut and terminate - <i>Crank Angle Sensor, on S5 EM harness</i>
1U : 1J
1V : 1H
1W : 1P
1X : 1G
Remaining pins/wires on transplanted S5 plug: "Connected to" - harness wire to find and where to find it.
1A: Battery - blue w/ red, pin 10, FEM-02 (Look close, the pin numbers are on the outer rim of the plug). Reroute&extend end only or splice into this wire. Do not cut off mid-way.
1B: Main Relay - black w/ white (NO DIAMONDS), pin 2 or 9, FEM-02. Splice into one of these wires for the ECU. It can be cut because the two wires become one after the FEM plug, but it's probably a good idea to keep power across both pins for...resistance-heat reasons? I guess? Only reason I can come up with.
1C: Starter/Ignition switch - Black w/ red stripe and silver diamonds, pin 3, FEM-02. Reroute&extend end only or splice into this wire. Do not cut off mid-way.
1E: MIL lamp is not on S4, <i>would</i> go to large blue nearby S5 Dash Harness plug at pin 20. S4 plug doesn't have it. You'll have to run this wire manually to an S5 warning light cluster if you really want it.
1K: Fuel Pump Resistor Relay - Used in S5s and S4 Turbos to reduce the fuel pump speed during idle and cruise, not found on the S4 N/A. I assume it can be left off without tripping limp home mode and the existing wiring will work fine without it. <b>If someone knows better, please correct me on this.</b> Ironically I have one kicking around, but since it's a six-pin connector, I'm going to avoid this for now.
1S: Fog light Switch - Since this is an input, almost positive this is for adjusting idle under extra load. Obviously optional. I'm not bothering with this right now.
Feel free to add anything important you want to, just refrain from comments about "this would have been easier if you just replaced the front cover and used all S4 stuff." Like I haven't read <i>that</i> before... If I'm doing it this way, there's probably a reason.
Last edited by Delphince; 10-18-15 at 04:21 AM.
Reason: Update
does cutting the s5 plugs on the s5 harness and adding s4 plugs to it work? i mean all 3 ecu plugs, so that you only swap the ecu.. and maybe leave out the omp wires.
i have an s5 vert i want to put the s4 turbo rtek in... my plan is just cutting and resoldering the 120 or so wires right at the 3 ecu plugs.. does this not work?? why?
does cutting the s5 plugs on the s5 harness and adding s4 plugs to it work?
To my knowledge, it's far worse. Going S4 to S5, the stock relocation and rerouting of certain systems means you end up with two of something, so it takes care of itself. Like I previously mentioned, the CAS is a great example. It comes down the Front harness on the S4 and plugs straight into the ECU, but comes down the EM harness side on the S5 and plugs straight into the ECU. That means going S4 to S5 (S4 front, S5 EM) you get two routings of the <b>specially shielded</b> wire bundle that carries the signal, with the second one all set and ready to go and the first left to hang. Going S5 to S4 (S5 front, S4 EM)...you'd have none, and would have to try and lay it into the wiring harness yourself from scraps. I'm sure that would just be the start of complexities that are even worse than what I'm working on.
Err, right, sorry, just reread and got that you suggested keeping the S5 EM harness. Uhh....not really sure. You'd still have to lay about 18 inches of shielded cables across the FEM plugs, and it avoids plugs for a reason. I mean of course anything is possible with enough work, but eesh, I wouldn't want to attempt it. Wiring in the resistor packs for the injectors and other such bits...
i wouldn't need injector packs, the s5 injectors are high imp.i know of others who run s5 AFM with the s4 ecu. so that works, i've got spare s4 ecu pigtails, i may just wire them in parallel so i can swap between the ecus.. a stock s5 ecu, should i run the s5 engine, or swap to the tunable s4 turbo ecu, and turbo engine..tunable means i can adjust for the s5 sensor calibration variances..
<i>Oh,</i> you really mean <i>just</i> the ECU. Err yeah, I guess so. It would just be wiring difficulties really. Best asked in another thread though, this is for an engine and ECU swap; I thought you were asking about the opposite. Whatever hiccups and difficulties you'd run into wouldn't be anything I'm coming across since you're attempting a different mix of hardware.
<i>Oh,</i> you really mean <i>just</i> the ECU. Err yeah, I guess so. It would just be wiring difficulties really. Best asked in another thread though, this is for an engine and ECU swap; I thought you were asking about the opposite. Whatever hiccups and difficulties you'd run into wouldn't be anything I'm coming across since you're attempting a different mix of hardware.
i was only suggesting a method that might be Easier, as you just noted..
if i was swapping an s5 engine and s5 ecu, into an s4 car. i would use everybit of the factory s4 wiring( is it noted to be better?) and i would chop off the connectors right at the ecu, and at the AFM, and swap any other incompatible sensor connector at the connector itself.. then you'll still have to add wiring for the omp, unless there is some useless emissions junk or that AWS wiring to convert to running the omp...
when i come down to the project i'll figure it out on my own and report back on the difficulty, but as i have had time to mull over the s4 to s5 swap of any sort. swapping ecu connectors always comes back to the easy way out, im not sure why others don't approach it the same way?? am i missing something or is it just soldering 80-or 90 wires is scary to some people?
I don't have an S4 EM harness. I'm not repairing or swapping in my car, I'm building one from practically scratch. The hull was junkyard body stripped and ready for crushing; I bought it, power-washed it down, and have been steadily ordering and installing components, including an S5 engine/drivetrain that came with an EM harness already on it. I don't have any S4 stuff to swap over other than what was already in the car attached to the interior harnesses.
So soldering connectors is what I'm doing, but with my setup I only need to replace the F31 and two FEM connectors. If I had two S4 harnesses and an S5 ECU, I'd need to replace all three ECU connectors, and still need to rewire the FEM plugs (even though they would connect) because the ECU wants things on different plugs. If I kept S4 everything except for the engine block, that would be the "easy" way everyone suggests whenever this topic comes up. But again, not an option.
But realistically, like you think, neither way is easier. They're just different. If you're more mechanically inclined, swapping S4 engine parts is easier. If you're into electronics and diagrams, plug rewiring is easier. But holy crap, there's a lot of homework for the latter. If it's all written down with clear instructions, it would be the easiest method IMO. But...no one's done that yet. They always flake out instead of writing it down for the future. Currently on my computer desktop I have six threads from rx7club.com and two from nopistons.com open, four pinout diagrams, three pages of handwritten "worksheets", two FSMs, two harnesses on the floor, one FEM color code diagram, and a partridge in a friggin' pear tree to try and figure this all out.
Not sure how extensions would help. The products offered stay don't splice different generations together, unless there's another part of the site I'm not seeing. Besides, splicing isn't the hard part, collecting the info is.
<b><i>Continuing on because I can't edit the old post anymore...</i></b>
That covers the F31 plug. Make sure all the splices are properly insulated, even the wires that were simply cut; you don't want to take any chances with an ECU. Wrap it up, and strip down around the two orange FEM plugs if you haven't already. The two plugs aren't directly next to each other like the S5's are, but they're not hard to find. Staring into the plugs, here's how they're numbered:
Normally I should orient those using the same idea as before: staring into the female port of a plug pair. But in this case, that wouldn't have you looking at the wire-side. So to avoid confusion, let's keep things familiar with how the F31 was handled. To restate, the pin mapping above is staring at the <b>wire side, clip "up"</b>. Now bring out the two-plug FEM bundle that you got off an S5 Front harness. Hopefully you cut all the wires to a similar length. To keep things clean, as you cut wires for the S4 plugs, snip far enough back from FEM-01 to be across from where you'll be cutting the wires to FEM-02. As before, make sure you have enough slack.
Start with the wipers. On the X-11 and FEM-01 plugs, you're going to find four blue wires. Three have stripes: red, yellow, and white, and the last is plain. Solder the corresponding wires, as before.
FEM-01 : X-11
1 : 14
3 : 3
9 : 18
10 : 9
Get the Ground next. Pin 5 on FEM-01 to pin 4 on X-10.
Next comes cruise control. I'll be honest, this is where things start getting iffy. The switches and units are set up differently, and the diagrams don't provide enough information on the workings of them to say whether or not a straight wire-up will work. On the S4, ignition power goes straight to the actuator and control unit in parallel along a green w/ yellow wire, on the S5 it goes through the unit before getting to the actuator on a blue w/ orange wire; it changes back again to G/y after the X-10 FEM plug; voltages are listed for the S5 but not for the S4, sooo...I dunno. I'll include what I've got if someone is more deft and less daft at sorting schematics. Either way, I'll suggest what I've got, though at this time I don't know if it'll work.
FEM-01 : X-10
7 : 1
8 : 8
14 : 2
15 : 7
Next, let's get the Main Relay from before out of the way. Pins 2 <i>and</i> 9 on FEM-02 get cut and spliced to pins 10 and 19 on X-11. Black /w white stripe, no diamonds along the wire. Order doesn't matter; they both connect back together before and after the plugs. Same goes for the power feed to the injectors. Pins 6 and 12 on FEM-02 get connected to 11 and 20 on X-11. Black w/ yellow stripe. Nice and easy. Just don't mismatch a yellow with a white.
FEM-02 : X-11
2 : 10¹
9 : 19¹
6 : 11²
12 : 20²
(¹ , ² - can be swapped)
Last edited by Delphince; 10-19-15 at 01:08 AM.
Reason: Update
I think the second hardest part of this whole endeavor is the false information sources. Many a forum thread had a person providing information, and others adding to or correcting that while making a simple mistake like <i>looking at the plug backwards.</i> As if this wasn't hard enough, it gets turned into a high school math problem of "Five people provide different information about an event. Three of them are lying. Compare their stories to deduce who is telling the truth." Ugh...
I think the second hardest part of this whole endeavor is the false information sources. Many a forum thread had a person providing information, and others adding to or correcting that while making a simple mistake like <i>looking at the plug backwards.</i> As if this wasn't hard enough, it gets turned into a high school math problem of "Five people provide different information about an event. Three of them are lying. Compare their stories to deduce who is telling the truth." Ugh...
yeah looking at the plug backwards, but also the 86-88 change some wire colors, and then have a larger variation between models at x-15 (i think). the S5 pretty much are all the same except x-10 and x-11 which add/subtract wires depending on models. as an aside the JDM S5 only has the x-11 plug, as the engine harness doesn't do wipers, and the pinout is actually closest to the US a/t car, as the JDM cars have only the one engine harness that does m/t and a/t, and in the US we have 3 different ones, m/t, a/t and turbo.
I'll just throw this out there without having any clue if the thought is relevant but, how bad is harness plug swapping on the other side of the bulkhead connection? Maybe one should swap the BC also and deal with the stuff on the other side?
yeah looking at the plug backwards, but also the 86-88 change some wire colors, and then have a larger variation between models at x-15 (i think). the S5 pretty much are all the same except x-10 and x-11 which add/subtract wires depending on models. as an aside the JDM S5 only has the x-11 plug, as the engine harness doesn't do wipers, and the pinout is actually closest to the US a/t car, as the JDM cars have only the one engine harness that does m/t and a/t, and in the US we have 3 different ones, m/t, a/t and turbo.
Mhm, which is why I'm trying to do this write-up by pin more so than by color.
<strike>While I have your attention, though, I think I'm down to the last of it, except I've misplaced my information on what to do about the two alternator wires (W/B pin 3 and B/W pin 11, FEM-01, S4). It was something about a signal for the regulator. You did this before with your race car, and I would really appreciate it if you could give me the cliffs notes on what to do about them in relation to having an S4 or S5 alternator. Otherwise I'm going to have hours staring at two charging system schematics ahead of me.</strike> Figured it out.
Originally Posted by TonyD89
I'll just throw this out there without having any clue if the thought is relevant but, how bad is harness plug swapping on the other side of the bulkhead connection? Maybe one should swap the BC also and deal with the stuff on the other side?
Not <i>entirely</i> sure I understand your question; do you mean replacing the S5 X-10/11 plugs with S4 FEMs? It would be pretty much the same thing; it's what Luciu$ did. You'd still be looking for the same wire colors on either side of the connection to match things up, still trying to identify what pin on both versions handles what circuit; the splice would just be different colors. I prefer using the S5 connectors because there are more pins slots available to add turbo bits in.
Since this is an N/A car, there's no wiring for your boost gauge. Thankfully, it's not hard to run, since the EM harness is already set up with them. There's a couple ways your can do this, but it's a good idea to have a plug and not try to just have a soldered connection between the two harnesses. You can either cut the wires on the EM side of the X-11 plug and add in your own little plug, or you can do what I did.
Scavenge two lengths of wire from one of the dash plugs on your donor S5 harness by using a paper clip to lift the tiny tabs and pop the male pins free from the plug. I used X-18. Insert these into the X-11 plug at the following places:
Pin 16: Boost/pressure sensor. Green w/ yellow wire on the EM side.
Pin 5: Boost/pressure sensor ground. Brown w/ black wire on the EM side.
Run these two wires to wherever you want your boost gauge. If you're trying to run the stock gauge, you're going to have to look for a pinout for the turbo gauge cluster, be it S4 or S5. It shouldn't be too hard to find, but I'd prefer to not spend the hours confirming and writing up whatever I find, especially since I don't have one. But those are your signal wires, do with them as you please.
Next the Circuit Opening Relay (the conflicting advice on this one, sheesh...). Pin 12 on X-11 to pin 4 on FEM-02. Brown to brown, go figure.
Water temp Gauge. Yellow w/ white wire on pin 1 of X-11 to the yellow w/ black wire on pin 8 of FEM-02.
Pin 11 on FEM-01, black w/ white and diamonds, is for the inhibitor switch if you have it. Cut and seal, unless you have an automatic. In which case, first I have to ask: _why?_ And secondly, I'd suggest asking about this one. I don't have an automatic so I don't see how it would hook up, if at all.
Pins 12 and 13 of FEM-01 are for the Sub-zero Starting system. Cut and seal the wires. You don't want this thing anyway. Even Mazda admits it was a bad idea.
Pin 1 on FEM-02, brown w/ yellow, is the Air Bypass system's connection between the relay and the solenoid. Cut and seal, the S5 EM harness handles it.
Pin 7 on FEM-02, green w/ black, is for the Water Temperature Switch Electrical Fan Subrelay. Cut and seal, the S5 doesn't have it, so now it's useless.
If you're going to keep things simple and run an S4 alternator, you can use most of the existing setup, but you're going to have to run two wires. Repeat what you did with adding the boost wires, and pick two empty slots on X-11 you know are clear on the EM side. I went with Pin 8 and 17. Install female pins on the EM side, and run these wires to your alternator. Connect the black w/ white wire to the R Terminal, which is the spade with an edge that points at the Mitsubishi logo in the center of the alt, and the white w/ black wire to the remaining L Terminal next to it. Refer to the attached file for pictures and other alternator installs, provided by jackhild59. You'll need to run the B Terminal "pole" straight to the battery. Straight to the battery (well, some kind of fusible link is recommended), not through the interior.
The remaining wires are idle control inputs that signal the ECU you have an electrical load turned on, in this case the headlights, blower, or defroster. This part is a mix of easy, tricky, and tedious at the same time.
First, pin 5 on X-10, the blower. It's a green w/ red stripe wire, and the easy part is you're looking for a green w/ red stripe wire that's very nearby to splice into. The tricky part is there are <i>several</i> G/R wires nearby, and only one of them is the one you want. Thanks Mazda. Look for a plug with eight wires on it about 18 inches further upstream; you'll find your wire on a corner. Splice into that one, and only that one. The others do not have continuity with your circuit.
Second, the headlights. Pin 11 on X-10, red w/ green stripe. This one sucks a bit, you're going to be running a long wire. Thankfully, I found a spot to splice into so you don't have to run it <i>all the way to the end of the harness</i> like on the actual S5. Still, it's going quite a ways. Run it down the harness to the steering column area. On the door side, you're going to find a blue 17-pin female plug, and you want pin 11. The pins aren't listed because it's female, but if you're looking at the wire side with the clip up, the numbers run right to left starting on the bottom row. Unwrap the wires, splice in. Do not use the other R/G wire on the clip instead.
Don't wrap up the bundle, because you're doing it again for the defroster. Pin 6 on X-10, black w/ blue wire, needs to be extended and run to the same plug you just used. Pin 1, black w/ blue as well, splice in.
Congrats. That's it. You're done. I haven't turned the key yet and I'm sure there will be a good degree of fiddling that will more than likely result in another post, but that's the electrical re-pinning.
One major final thought I have about this whole thing is that—with all do respect—people that respond with "read the FSM" to wire color questions can go jump off a $%&#ing cliff. You know what the FSM helps with? When you already have a wire identified and want to know where it goes and how the system it's a part of works. Trying to use it to identify a pin or wire color on anything but the ECU is almost completely pointless. The plugs show wire colors to pins, but they have no directory from that. There is nothing to tell you where in the 150-page book you're going to see that plug pop up with your wire color leading out of it, and even if you do scan page, by page, by page playing Where's Waldo, some of the plugs have more than one wire coming out of it with the same color code. They may be part of the same system, but if they don't share continuity, good luck figuring out which part of the system it is. The only way it is any good, at all, for discovering whether the wire you're staring at has to do with the sub-zero charging system or the injectors is if it's two different colors on either side of the plug that you've also identified already. <i>That</i> is usually a unique situation and removes ambiguity, and you say "hey, this page I stumbled onto is the page I want." But still, you gotta find the damn thing with your eyeballs, very slowly scrolling though, looking for the little dude with the striped shirt and cap. I did most of this work by comparing meticulously hand-traced wires with pages and pages of scattered answers that people gave, actual answers, not "read the FSM" answers, and even though some people were still completely off the mark, they pointed in the right direction.
Without that, the FSM is a pre-internet library with no book titles. The answers are there, but good luck finding them in the absence of CTRL-F.
Thanks to Satch and Luciu$ for being on the ball with solid information over the past decade.
Last edited by Delphince; 10-21-15 at 03:24 PM.
Reason: Update
i just dealth with this... and just swapped a s5 harness into the car. pinouts are so much different between s5 and s4 harnesses. just my two cents. converted the entire s4 car to s5. s5 ecu/harness, car harnesss, charging/starting harness.
sorry to threadjack total car noob here. so i have a s5 turbo engine, just looking for a good shell to put everything into. all the decent shells that have been popping up lately are all s4's. could i use a power fc to wire everything and run well? my friend has one that i could get a good deal on.
Finally posting the aftermath report. I expected stuff wouldn't work perfectly and I'd possibly need to make some corrections or additions.
Instead, it worked perfectly.
After unsticking the very-stuck injectors, she fired up and purred like a kitten, and went out for her first test run a few days ago.
...I've created a monster. Between the ultralight racing flywheel, 5-inch independently-wastegated downpipe, and grabby clutch, she's very touchy about rolling from a complete stop, but once she gets moving...good god. I can't WOT the throttle under 3rd gear, she just spins tires even with 225s on. I'm in love if I can get a leash on her.
A couple thoughts and a correction, though. First the correction. I made a typo in post #11 in dealing with the wipers. Hopefully anyone doing it themselves would have noticed going by wire colors, which is why I included those as well. Anyway, this was what it should have been:
FEM-01 : X-11
1 : 14 2 : 3
9 : 18
10 : 9
If you decide to use an S5 alternator, don't use the stock wiring. For one, the ring terminal on the S4 wiring won't fit onto the larger post on the S5 alt, and for two, you need a much heavier-gauge wire. 6awg is recommended. Follow the instructions in the image attached above, and don't fudge the S-terminal by connecting it to the B-post. It must connect to right after the battery on a separate line, otherwise it won't notice the slight drop in voltage the alternator will be receiving because of real-world physics, and it won't charge your system correctly.
There was also a useful bit of info I came across in dealing with the MAP sensor. Hopefully you got the correct one, but in the event you grabbed an S4 turbo sensor (n318), you'll note it has four male tabs in the plug as opposed to the S5's three. Run ignition-sourced +12v to that pin and it'll work. I don't know how perfectly the mapping matches the S5 version, but so far it's been working just fine for me. Yes...I had an n370 sensor, and I lost it in the move from NC to Oregon, somehow. Bugger. I used the +12v source that used to run from the FEM plug to the S4 alternator, since I converted to an S5. Pretty convenient.
Have fun, folks. I'm going to go get arrested just trying to grocery-run a jug of milk.
10-17-15, 06:28 AM
