EJ25 SOHC ECU difference for manual or automatic transmission?

[Chr]

Hey guys,

first of all I need to confess:

I don't really own a complete Subaru (sorry) ...

 

Last year, we swapped a Subaru EJ25 SOHC engine from a 2000 Legacy (156 hp) into our 1973 VW Beetle.

We also installed the stock ECU and all the necessary parts from the original wiring harness.

 

Combined with a 5-speed manual gearbox, a lighter flywheel and a custom exhaust system, the car produced 187 whp on the dyno. It is really fun to drive and nobody even remotely expects this kind of power in an old VW Beetle...

However, the ECU constantly reports error code 38 "Engine torque control" or "Torque permission signal". When I checked the ECU with OBD2, I found values for "Engine Torque Request", "Torque permission signal" and some more stuff that leads to the conclusion that the ECU is expecting to have a Subaru automatic transmission with the corresponding TCU connected.

I bought another ECU that was confirmed to be out of a car with manual transmission, but after installing it, I got exactly the same behavior and the same error codes as before.

So there are two options:
1. Someone screwed me over and the new ECU is again out of car with automatic transmission
2. The ECUs are actually the same for AT and MT and the transmission mode is set somewhere else...

For the older engines 1996-1999, I found some information about a "AT/MT identification pin" on the wiring harness, which defines whether the ECU should behave like AT or MT.

Does anybody know, where to find that pin on my ECU (2000 Legacy, EJ25 SOHC 156hp) or if it even exists?

I checked multiple websites for ecu pin-outs or wiring information, including this forum and also this one:
https://hackedecu.com/ultimate_subaru_pinout

... but I did not really find anything useful for the 2000 Legacy...

best,
Chris

[ccrinc]

When you do a swap like that, you need to modify the wiring harness so that you eliminate everything except that which makes the engine run.  There is absolutely no need for your car to even know that there's a difference.  I suspect you left some of the wiring in that would pickup that signal. Of course, the VW has no way of sending it.

 

PM me and I will send you the information to the only place I know which sells the wiring diagrams for modifying the harness for that style of engine so you can permanently correct the problem.  We do VW conversion engine setups all the time, so I know exactly what you're talking about.  (If it was me, I would have recommended the '90-94 EJ22: must less expensive, less hassle and only a 25-30hp difference. But you've already done the job, so...)

 

SWEET bug, BTW!

 

Emily

 

ps: we shipped an engine to Darmstadt last year!  Small world.

Edited February 27, 2016 by ccrinc

[Rooster2]

From the conversion, that is  a sweet looking conversion. Off topic..........where is the radiator placed, in what was originally a water cooled bug??

[Fairtax4me]

I took a look at the diagrams I have for 2002 model year (should be similar enough) and the only thing that stands out in the diagrams is a communication line between the ATCU and the ECU.

 

I suspect there should be an identifier pin on the ECU that needs to be grounded, similar to the older model years, but the diagrams just aren't showing it. There are similar instances of unlabeled pins being used among other projects people have done, such as the Sport mode pin on the TCU in 95-98 model years.

 

I think the thing you'll have to do is get a wire harness from a manual transmission car.

There may also be the option to have the ECU flashed in order to disable those codes. This is something the performance crowd does fairly often when removing certain components from the turbo engines and/or when doing turbo swaps into non-turbo cars. I'm not sure of specifics as to what you need in order to do this. I imagine having it flashed by a performance shop would cost a few hundred $$.

[ccrinc]

I took a look at the diagrams I have for 2002 model year (should be similar enough) and the only thing that stands out in the diagrams is a communication line between the ATCU and the ECU.

 

I suspect there should be an identifier pin on the ECU that needs to be grounded, similar to the older model years, but the diagrams just aren't showing it. There are similar instances of unlabeled pins being used among other projects people have done, such as the Sport mode pin on the TCU in 95-98 model years.

 

I think the thing you'll have to do is get a wire harness from a manual transmission car.

There may also be the option to have the ECU flashed in order to disable those codes. This is something the performance crowd does fairly often when removing certain components from the turbo engines and/or when doing turbo swaps into non-turbo cars. I'm not sure of specifics as to what you need in order to do this. I imagine having it flashed by a performance shop would cost a few hundred $$.

You guys are assuming that you'll use the entire wiring harness.  NO.  You're overthinking it.  There is no way for a '73 VW transmission to communicate with a 2000 Subaru harness.

 

Don't worry about the pins: as I said before, all you need is the part of the wiring harness which makes the engine run.  When we modify a harness we start with the entire, 27+ lbs. harness and when we're done, it's about 7-10 lbs. 

That said, the harness, engine and ECU should all be from the same vehicle.  That way you  are assured that all components match up.  It's much more difficult to mix and match components.

 

VW/Vanagon conversions are a significant part of our business.  We do the conversions on the 2.2 harness, we outsource the 2.5 ones to a guy in Canada who is the well-known authority on these for N. America.  (Besides, we've done 2.5 harnesses and it's just not worth our time due to the amount of effort which it requires.)

 

With all due respect, this is kind of "our thing".   People tell us all the time that they've seen our name on various VW conversion forums and because of that, came to us.  Many of our customers are shops which specialize in conversions.  I won't say it's easy, but keeping it simple (KISS) is the way to go here.

 

Emily

[Chr]

Hey guys,

thank you for all your replies.

 

We solved the problem...

The identifier pin for that ECU is B135 - Pin 25

Wiring it to ground did the trick.

My ECU is now in "manual mode" and all my error codes are gone.

All the wiring diagrams and pin-out tables I had so far were from AT cars, so the pin was not even listed.
 

Of course, we stripped the original wiring harness and removed everything we do not need for our beetle.

Unfortunately, for the AT wiring harnesses, there is not even a wire connected to that pin, it is just empty. So there was nothing to remove from the harness.

We had to add a new wire to that pin and wire it to ground.



Additionally, we had to un-wire the neutral switch B135-26, since the ON/OFF state is switched between AT and MT.

Otherwise, my engine would start reving up as soon as the ECU gets a speed signal...



Best,
Chris

 

p.s. The radiator is placed in the front where the spare tire used to be.

[Fairtax4me]

Good deal! Glad you found it! Happy Beetling!

[ccrinc]

Oh man, what I wouldn't give to drive the Autobahn again! Or the Italian Autostrada.