Subaru Forester Owners Forum banner

2005 - How to ► wire your 4EAT to 5MT swap!

90364 Views 106 Replies 25 Participants Last post by  krausenoel
6
so, you've completed the mechanical part of your 4eat to 5mt swap and are stumped with the wiring. well, you've come to the right place. if you're able to get the complete bulkhead dash harness, do it (along with the 5MT ECU). otherwise, read on...

since i haven't been able to find anything clear online to be completely successful, i ordered me the FSM and picked my brain with a ton of wiring diagrams. i'll only be explaining my process as done on my 05MY FXT. though, the premise of this process should apply to other models as well.

for the wiring underneath the car and to keep things plug-n-play as much as possible, i reused the existing 4EAT harness and repinned as much as i could.


left: 4EAT sensor harness with the three sensors (torque converter turbine speed, front vehicle speed sensor 1, rear vehicle speed sensor 2)
right: 4EAT harness for inhibitor switch

i'm on a 5MT ECU, now. but even when i was running the 4EAT ECU, i still was not using the 4EAT TCM and was able to get around town. no matter what combination of those three plugs i had plugged into the TCM, my OBD-ii port wasn't functional. i couldn't use either my AP or a code reader tool unless i removed the TCM. so, i left it out. because of this, instead of running separate wires from the tranny into the cabin, i reused what wiring was already there that ran between the tranny and the TCM.


the following items are what will need to be tackled:
  • key interlock switch
  • clutch switch
  • reverse light switch
  • neutral safety switch (nss)
  • vehicle speed sensor (vss)


here's how to read the pin numbers for the Male and Female plugs...





key interlock switch
so you can remove your key from the ignition, you'll need to jump (forgot what pin numbers) the black and the white wire. i reused the wiring from the 4EAT shift lever assembly that included the lightbulb...




clutch switch
i used this so i can start the engine like on any other MT vehicle. from the clutch switch, i ran a couple wires down to pins 11 and 12 of the 4EAT inhibitor switch harness. this is to mimic Park/Neutral. (this is the only separate wiring i ran. i'm sure i could have used existing wiring like i did with my vss process, but that idea came later. and there were enough wires left to do so.)


reverse light switch
reverse switch and nss are joined to a 4-pin connector. i repinned 2 and 4 to pins 9 and 10 of the 4EAT inhibitor switch harness coupler.


neutral safety switch (nss)
reverse switch and nss are joined to a 4-pin connector. i repinned 1 and 3 to pins 1 and 4 of the 4EAT inhibitor switch harness coupler.


vehicle speed switch (vss)
(NOTE: it's important to understand that i'm using the wiring that ran between the tranny and TCM as a way to avoid running my own separate wiring. because of this method, i highly encourage not plugging in the TCM!)

the 5MT vss has three wires (signal, ground, power)...
speed sensor 1 of the 4EAT sensor wiring harness has two wires. i used one to run signal up to the cabin; the other to run ground up to the cabin. the speed sensor 2 of the 4EAT sensor wiring harness has three wires. i used one to run power up to the cabin. that covers all three wires of the vss up to the cabin.

vss pins (sensor on tranny):
pin 1 // signal
pin 2 // ground
pin 3 // power

4EAT sensor wiring pins (reused harness from inhibitor switch):
pin 14 // speed sensor 1 signal used for vss signal
pin 18 // speed sensor 1 ground [this wire is shielded to ground as well] used for vss ground
pin 9 // speed sensor 2 blahblahblah used for vss power

those three lines run up to the middle plug (medium-sized) that plugs to the TCM. (REMINDER: you're not to plug the TCM!)


^
tap from B55 plug (middle plug)
pin 6 // signal line
pin 15 // ground line (just ground this to chassis)
pin 24 // power line


^
to B56 plug (larger plug)
pin 1 // signal line (runs directly to both speedometer and ECU)
pin 31 or 21 // +12v IG ON line

(should you decided to keep the TCM, starting from the vss, you'll have to use another ground and power source. for the signal, you may still use pin 14 of the sensor wiring harness. for the MT, the speed signal goes directly to both the speedometer and ECU. for the AT, the speed signal goes to the TCU first, then to both speedometer and ECU.)



(this post will be updated as needed to better clarify exact plug identification pin/wiring colour, etc. as i go back and review diagrams, notes and pictures.)
See less See more
  • Like
Reactions: 1
41 - 60 of 107 Posts
Only thing i havr non functional is abs which is causing in operability of cruise control. I think i know a work around but have been too lazy to desl with it. Otherwise i have no codes on my stock auto ecu with a 6MT
So i havrnt sifted through all this but from the beginning when your obd2 port wasnt functional its because of the plug from your shifter in the car has an ignition inhibitor switch. If you dont jump it out or plug in the shifter temporarily, the ign on circuit on obd2 will not function making a flash tool think car is off......you may have already gotten by that...sorryif its covered.
^
all i did was pull the TCU out, and it worked. it also solved the wacky idling and shifting issues i was having by keeping the TCU in.

For the speed sensor, i used the three wires from the origonal speed sensor harness that went to the rear speed sensor....theres 3 on your tranny....one to ground (which there is a spot for on the old harness, and the other two to the speed sensor. My odometer works just like normal on my 09 with an 04 6mt.
^
those sensors on the 6MT are very similar to the 4EAT in comparison to the 5MT and 4EAT.


Only thing i havr non functional is abs which is causing in operability of cruise control. I think i know a work around but have been too lazy to desl with it. Otherwise i have no codes on my stock auto ecu with a 6MT
^
are you CAN-BUS btw?

my CC works. idk about ABS. i haven't tried it out. i'm still actively looking for a bulkhead harness for my year anyway.
I'm canbus. So there are definitely a few differences in model year details. Tcu made 0 difference in or out of my car once tranny was removed.
4EAT to 6MT WIRING CONFIRMED!!! This is a universal write up for 4eat to 5mt as well as 6mt. Just completed my swap and it works flawlessly.
Howd you get the ABS to work on an SH? Thats the only thing i have left to figure out for my 6mt. Other thsn that it works fine.
My ABS never worked from the day I bought the car...I just took apart the cluster and removed the LED for abs and the brake light...

Still working on cruise control as it doesn't work on mine yet...
Cruise wont work if abs isnt functioning....unless theres a way to bypass the inoperable abs signal.
Regarding the ABS issue: I'd assume the ABS module would only need power, ground, ignition power and a VSS for inputs for the tranny side. I'f I get bored tonight, I'll look over a SH schematic and see what can be done.
False. Prior to the swap my cruise control always worked even though the ABS was not working..However, I am interested as to how to get my cruise control to work..
Perhaps not for the earlier foresters but for my SH doesnt want to work without ABS. The earlier year and newer years have some completely different comms and wiring procedures in that department.
4EAT to 6MT WIRING CONFIRMED!!! This is a universal write up for 4eat to 5mt as well as 6mt. Just completed my swap and it works flawlessly.
^
glad to hear. congrats!

False. Prior to the swap my cruise control always worked even though the ABS was not working..However, I am interested as to how to get my cruise control to work..
^
i have an ongoing timing issue due to my lightened flywheel which i don't have the time to get a tune for. but every time i've had a CEL for any sort of issue, i've noticed it always kept my CC from ever working. did you never have any CEL with your non-functioning ABS prior to your swap? and do you have any CEL codes, now?
None prior...worked fine. Abs on now and no cruise.
Dang, I found this thread after I mapped out my MY06 4eat -> 6mt swap!
I doing mine slightly different, I'll post up my notes and pics once it's finally done. If it works.


Just to confirm, the AT ecu works just fine for the MT conversions?
G
It works, but it'll throw codes, including an ATF temp code that'll make your radiator fans run on full blast all the time. It will also lock you out of your ECU if you're trying to tune it. The latter was fixed by removing the TCU.
I am stuck on the vss. I have tried to moving pins around to get it to work and nothing! I dont know if i am reading the pin out wrong or what the deal is. I am reading the harness that is the female end 1-2-3 but i have seen other places that it is 3-1-2. It is on a jdm v7 6speed. If i am reading 1-2-3 it is gw-gy-gb. The TCU is removed and pin 2 is ground in the engine bay. I didnt see the point in bring it into the cabin via 4eat harness.
Seems like 1 of the pins is supposed to be grounded and the other two hooked up.

I know mines not the same but i believe green black on mine i grounded and the othertwo i hooked together.
The thing i find odd is that i am not getting a low vss voltage cel anymore. I can mov the pins around at the sensor plug but no combination worked unless i havent taken a large enough sample. Ie i only drove around a small block but i noticed the OP said it took a few miles to register. I drove 180 miles as he has diagramed. Nothing.
Anyone know what pin on the AT ecu to ground so that it thinks it's a MT?
Vss works! This write up is perfect! Needed a new speed sensor! Confirm a v7 6mt into an 05 forester xt! Thanks for the write up!
woohoo! and congrats!
41 - 60 of 107 Posts
Top