ive been helping a friend do a manual swap on a 2004 h6 outback. at the moment the engine and trans are in the car the auto gear selector is plugged in and in neutral and have the shift switch bypassed so can remove the key. it runs and drives but it runs very poorly. would the tcu not seeing the transmission cause running issues? from what i understood the car wouldent be happy not seeing the transmission and throw lights on but i thoght it would run normal. yes the plan is to wire the manuals speed sensor in and get everything working but we thoght it would run better than it does. the engine ran great before the swap but it was also torn down and had new head gaskets and timing stuff put in. it seems to run really nice for moments then runs like crap and stalls but starts back up runs good then bad back and forth

Edited February 18, 20206 yr by sirtokesalot

Would search and post over on LegacyGT.com.

There are a few who have done this over there and should be able to offer aid.

O.

well my friend had many things happen today. he found the cam sensor was actually not fully plugged in and when he plugged it in the engine started running great. built a resistor pack to fool the tcu still getting p0866 TCM Communication Circuit High code so far its the only code its spitting out would anyone know what the ecu wants to see from the tcu to not set this code?

Found this

https://www.obd-codes.com/p0866

O.

3 hours ago, ocei77 said:

Found this

https://www.obd-codes.com/p0866

O.

yea ive been through alot of what i could find on google. the standard code descriptions are not too helpful here as they are saying what could be wrong with the automatic transmission and in this case there is no automatic transmission in the car. its a manual now.

On my H6 I still occasionally pop this code. I am running with the resistors, and it is not consistent. I suspect there is a second circuit that occasionally requires an input, that I have not found due to its infrequent 'poping' of the code. 

Please keep informed what you find. I have most the wires mapped on mine, still haven't found it, ha. 

Join the group "Six Swapped Subarus" on Facebook. There's a couple guys there that have decoded the ROM to delete the auto transmission related code.

4 hours ago, charles_thomas said:

On my H6 I still occasionally pop this code. I am running with the resistors, and it is not consistent. I suspect there is a second circuit that occasionally requires an input, that I have not found due to its infrequent 'poping' of the code. 

Please keep informed what you find. I have most the wires mapped on mine, still haven't found it, ha. 

so far havent found much we wired in the reverse lights and speedo today as well as tidied up some of the other wiring. the code comes on currently every 3 starts on his and were not sure if the resistor bank we built is correct.

I personally do not Facebook. The ROM has a manual setting that is used overseas (if you have the correct ECU). Some can be easily "switched" to this by sending the correct signal on the correct wire. Commonly grounding it. Messing with the programming of the ECU to simply delete a code or error light OFTEN results in other problems that are neither noted or observed by the casual mechanic, sometimes not rearing their ugly head for years to come.

I did not happen across one of those handy ECUs. I have also noticed that the Pinout and ROM change slightly each year, making a static mapping of the pins mostly useless, the resistance of the solenoids and return circuits will also vary based on component physical location, making finding the correct resistance to "fool" the ECU a bit of a trial and error scenario.

I had to increase the resistance a couple times, on a couple circuits, to have the ECU respond as though the circuits and components were still there. 

I would recommend adding some more resistance to the circuit and see if it helps. I am in the process of doing that now with mine, and does seem to reduce the number of times the code blows. I'm still skeptical that there isn't a secondary reading the ECU gets from some other component that I do not have, as my engine is running completely standalone.