Subaru Forester Owners Forum banner
1 - 5 of 5 Posts

·
Registered
2009 Forester XT, 4EAT-->6MT, 2008 STI Brembo
Joined
·
4 Posts
Discussion Starter · #1 · (Edited)
Firstly, Mods feel free to suggest a different forum if you feel this would be better suited somewhere else! This is primarily an electrical question but it is related to a transmission swap so I thought probably here but also maybe in transmission stuff.

The TLDR: Manual swap into 09FXT, mostly works, however I have a persistent P0600 code. Grounding ECM B136,Pin15 does not work. Suspect maybe the dual AT/MT map on most models does not apply to the 09FXT since they were AT-only. I have went as far buying and swapping in a MT 08-12 WRX gauge-cluster, key / key barrel, Integrated body control unit, ECM, and keyless entry antenna set. Did the necessary NPS and Clutch safety switch groundings, but something is still triggering the immobilizer and not allowing it to crank/start. At this point I would prefer to keep the WRX stuff since it looks nicer but probably going back to the FXT parts until I get this figured out. Read-on for more detail.

So recently took the plunge and swapped in a 2015 STI 6MT into the 09XT. Took more time than I thought it would but what project like this doesn't 🤷‍♂️. Anyhow... SUCCESS!.. mostly.. Many thanks too Superacerc's excellent writeup: ('09-'13) - 6 Speed Transmission swap details

As of this writing I have driven the swap about 400 miles and it seems to work fine, however despite my best efforts to diagnose the electrical requirements I was unable to fix a CEL P0600 code (because the automatic is no longer connected). This of course disables CC and also traction control which is of more imminent concern where I live. According to my research grounding ECM Plug B136,Pin15 lets the ECM know its driving a manual and, as I understand it prevents the dash code. When I tried this, I got a security light flash and the car refuses to crank / cranked poorly but wouldn't start, unplugging this pin resolves the issue (but still have CEL). At the time I did not think to try ground the neutral position switch (NPS) and the clutch engagement switch pins (B136,Pin31 and B136,Pin25) on the stock ECM. Finally, I tried unplugging the ABS control module completely as a stab in the dark but this had no effect.

At this point I believed the issue may be that this model was never sold with a manual option, and even though the ECM pinout seems to be the same, there is no map/software to handle this case in the 09XT. So I bought an 08-12 (unsure of the exact year) MT WRX, ECM, integrated body control module (BCM), key / key barrel, keyless entry antenna, and gauge cluster as a VIN-match set from a donor car. I installed all these parts which was pretty much PNP, except the keyless entry which I left unplugged due to different connectors. I grounded the neutral and clutch switch pins, and it will not crank/ cuts power ignition powered items (like aftermarket gauges) when turning the key to the crank position. So it seems like something is still triggering the immobilizer even though, assuming the parts are matched, I believe they shouldn't cause a security issue on their own (ie due to being from different VINs).

Summary of things I have tried so far:
WITH ORIGINAL ECM, dash, BCM, key etc:
  • Grounding ECM B136,Pin15 --> security light / no crank / intermittent crank with no start (did not have NPS and clutch engagement grounded)
  • ABS control module plugged/unplugged --> no effect
WITH 08-12 MT WRX ECM, dash, BCM, keys etc:
  • Installed above parts except for the keyless entry antenna: with the original antenna plugged/unplugged --> no effect (except keyless entry stops work with original key fob)
  • Grounded NPS and Clutch switches (safe start) --> no start
  • ABS module plugged/unplugged --> no effect
Any advice/ideas on where to proceed would be appreciated.
Thanks in advance!
 

·
Registered
2010 FXT
Joined
·
16 Posts
@Sassquatchfour, could you please provide any insights on how or if this issue was resolved? I think a lot of SH XT owners want to do this swap but the electronics is by far the biggest challenge. I’m curious if anyone has gotten ABS (at the very least) and ideally VDC & TC to work with the 6 speed swap. Thanks
 

·
Registered
2009 Forester XT, 4EAT-->6MT, 2008 STI Brembo
Joined
·
4 Posts
Discussion Starter · #3 ·
@Scbsnx, I was just about to go out and tinker on this some more this evening. Again, most of what I know is from Superacerc's swap, I will refer to his experiences when considering my findings and have noted differences as far as I can determine. As I understand it, he had no dash lights on at the end of his build.
TLDR, I have not found a definitive answer for my specific issue, but regarding the swap when keeping the original dash equipment in place the basics of my findings are thus:

0) Restatement of the exact symptom presentation: CEL (P0600 code, short/ serial communication failure ) (subsequent blinking cruise), VDC/TC disengaged light, ABS light, and every 20th start or so I get a blinking red/blue temp light with the MPG monitor not functioning correctly (restarting the car solves this)(this indicates a communication issue). Overall, the CEL is annoying but doesn't really bother me on a day to day basis. Having the VDC/TC system working would be nice in the winter and when I am driving too fast on secondary roads (which I do a lot). Ditto the ABS.

1) The engine does not care about which transmission is behind it: I.E. the ECU does not rely on the TCU to keep the engine running normally. I have driven about 5k on the swap at this point and get similar mileage on the highway and even pretty solid increases around town. No rough idle, surging or other problems of any kind related to the engine. I am running a bone stock ECU flash.

2) The primary electrical modification "needed" to start and drive the car is the grounding of the parking pin on the automatic gear selector harness. This is ideally done by connecting it to your clutch switch, but.... it can also just be directly shorted so the car is "permanently in park".
This is one place I may experiment with by making the parking wire a momentary connection (via the clutch or some switch for the time being) and then subsequently shorting the "drive" position switch once the car is started. I doubt this will solve the issue as the lights (VDC/TC, CEL, Cruise) would likely be on no matter what position the automatic gear selector is in for another arbitrary code not related to disconnecting the transmission. Also Superacerc's swap did not run into this as far as was reported.

3) This doesn't mean the ECU is totally divorced from the TCU,
the ECU definitely receives a number of diagnostic signals from the TCU about torque converter turbine speed, front/rear speed sensors, temperature, etc. In principle (although I am not 100% sure), there would not be any faults present if you were to ratchet strap your 4EAT to the roof and plug in the electrical connectors with some extensions and leave the gear selector plugged in on the passenger seat. The transmission isn't doing anything, but the ECU is happy because it gets its precious data as expected / no shorts.
This may seem a little obvious (I.E. not changing the electrical system avoids problems), but my point is that the electrical problems are superficial and that it should be possible to spoof the "normal" conditions although perhaps a little tricky to actually pull off.

4) Following from point 3, one considered possibility for the P0600 "short/ serial communication failure" is that the ECU expects a signal (although it doesn't really care what signal exactly) from the 3 different speed sensors in 2nd gen 4EAT (torque converter turbine speed, front/rear shaft speed sensors). In fact beyond a temperature sensor, these are the only signal generating components of the 4EAT transmission; the rest of the wires are simply a voltage OUPUT to various shift solenoids which are dumb electro magnets. These speed signals would be in the form of pulse-trains (PWM signals) generated from hall effect sensors w/ magnetitic cogs/encoder wheels). Presumably, any range of pulse speed will work/is expected, but an open loop "short" (as in the case of being unplugged) may trigger a fault code due to abnormal voltage sensed by the ECU. I have tested whether plugging in the 3 speeds sensors from the transmission would solve this issue but it did not, these things can be sensitive to electrical interference and my connections were a little jerry-rigged but tested OK with the volt meter. I am about 90% sure that this alone is not issue, however could be a component with something else. Superacerc's swap used a 2004 6MT with a transmission speed sensor which is not found the the 2015 6MT I put in my swap.

5) The speedometer does not need the transmission and gets vehicle speed as the average of each wheel's speed via the wheel speed sensors --> the abs control unit --> ECU --> Dash computer.
Here enters one potential complication, I had to replace my rear hubs during the swap (because I'm dumb and damaged them during a concurrent Brembo swap). Anyways, I used aftermarket MOOG hubs because I did not want to wait another week for Subaru parts. One reported problem with the MOOG hubs is that the wheel speed sensors don't work (and consequently ABS/ VDC will not have enough information to function, re the dash lights). The best way to eliminate this would be to change them out for the Subaru parts, but they're basically new parts and my wallet says no! so it has languished.
So in conclusion, the ABS /VDC light may be unrelated but its impossible to tell and I should probably just bight the bullet and replace them with Subaru parts just to eliminate the possibility or maybe even that part of the problem.

6) As mentioned previously, there was never a manual model for the 09-13 XT. Most models have dual ECU flash but I am unsure what flash the XT used (maybe the same as WRX?, probably similar but tweaked). I have no idea whether this theory holds any water and have debated buying a flashing tool and an access port at some point. Superacerc's swap was on an N/A model I believe and therefore it definitely had a dual AT/MT ECU flash.

7)
Grounding MT/AT mode pin on the ECU (ECU Plug B136, Pin15 according to Subaru tech docs). The car will not start with this pin grounded, and in Superacerc's swap, (i think around post #80, he mentions this seems to not matter after working out some of his immobilizer issues.

8) Lastly, I purchased a complete set of a secondary 2012 WRX manual dash cluster and ECU + BCM, ignition, keyless antenna. My thought was maybe that I could swap it all in, have a known manual ECU, and get the nicer WRX cluster to boot. No dice, immobilizer issues prevent the car from starting, which is probably due to VIN matching with some other component or perhaps unknown differences in the wiring harness. This is still something I would like to do someday but the best option is probably to purchase a new gauge cluster and have the dealer do a VIN / odometer programming.

So if you're reading this congratulations on digesting that wall of text. If I ever figure this out I will definitely post it here. I also want to put together a few notes from my own swap experience at some point but feel like its not really a finished project I can recommend fully yet/ there are other good references out there already.
 

·
Administrator
2007 Forester Sports XT 4EAT
Joined
·
42,038 Posts
@Bang2021 welcome to the forum from Oregon!

Note that @Sassquatchfour last signed onto the forum 4 months ago. You could send the member a PM - Private Message... now called a "conversation" on this new site. The member is optioned to receive an e-mail notification, so you could receive a reply to your question.

Also... please complete your "Public Profile" - add your vehicle details!
Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]
 
1 - 5 of 5 Posts
Top