Phase 2 ej25 to ej22 swap. O2 sensor issues

[fuelforwar]

Hey everyone. Been searching without much luck for some info on an 02 sensor problem. As a little back story, I spent a year rebuilding a 2001 impreza wagon L with the ej222. After having it back on the road I was in an accident that totalled the vehicle. A couple years later my neighbor made a deal with me and gave me a 2002 bug eyed impreza that had a blown ej251. I swapped in the ej222 as a complete unit (didn't swap intakes or anything), swapped the computer, and the exhaust. Engine starts right up but I got multiple codes for the 02 sensors. Swapped both of them out but continue to keep getting P1132, P1133, and P1139. I've inspected the wiring and it seems to be fine. With a test light I'm getting power to the plug that feeds the 02 sensors. I noticed the 02 sensors are different between the two vehicles. On my 01 it was a 4 pin, and on the 02 it's a 6 pin, but the 02 sensor only has 5 wires. Do I need to repin the plug or change out the wiring to my sensors? Been struggling to find the right diagrams that matches my wire colors. Any help or input would be greatly appreciated. Thanks

[el_freddo]

Which O2 sensors are you running? I’d say they need to be matched to what your engine management system was running before the swap. 

In my mind that would resolve these O2 sensor issues you’re experiencing. 

Cheers 

Bennie

[idosubaru]

You want all the sensors to match the original wiring/ECU.  Just change the engine and nothing else.  Leave the original oxygen sensors, etc.  There's no need to count pins, just leave the old sensors in or replace them with the same part. 

Is that what you did?

[fuelforwar]

2 minutes ago, idosubaru said:

You want all the sensors to match the original wiring/ECU.  Just change the engine and nothing else.  Leave the original oxygen sensors, etc.  There's no need to count pins, just leave the old sensors in or replace them with the same part. 

Is that what you did?

I'll try to clarify this, the car everything is installed in now is an 02 impreza wagon T.S that originally had an ej251. The donor car was 2001 impreza wagon L with an ej222. I swapped over the ej222 and the computer for the one that was with the ej222. The main harness from the engine bay to the computer and 02 sensors are still from the 02 impreza. I replaced both front and rear 02 sensors with new ultrapower brand ones from rock auto.

[fuelforwar]

My biggest concern is, it looks like the 02 is a wide band 02, and the transplant engine was using a narrow band sensor. Everything I look up tho shows the 02 impreza should be a narrow band. However my scan tool shows it getting 3.7v and a lamda reading of 9.999. If it was narrow band it should be showing voltage of .1 to 1.0v

[idosubaru]

12 hours ago, fuelforwar said:

I'll try to clarify this, the car everything is installed in now is an 02 impreza wagon T.S that originally had an ej251. The donor car was 2001 impreza wagon L with an ej222. I swapped over the ej222 and the computer for the one that was with the ej222. The main harness from the engine bay to the computer and 02 sensors are still from the 02 impreza. I replaced both front and rear 02 sensors with new ultrapower brand ones from rock auto.

Reinstall the original EJ25 ECU and EJ25 intake manifold and EJ25 oxygen sensor. You did too much work for no reason.

If the engines aren't both from an automatic or both from a manual transmission then swap the EJ25 drivers side cam and crank sprocket onto the EJ22. 

Follow those steps above and you're done.  Have a question....reread the directions above. 

 

12 hours ago, fuelforwar said:

My biggest concern is, it looks like the 02 is a wide band 02, and the transplant engine was using a narrow band sensor. Everything I look up tho shows the 02 impreza should be a narrow band. However my scan tool shows it getting 3.7v and a lamda reading of 9.999. If it was narrow band it should be showing voltage of .1 to 1.0v

More wires just has higher fidelity and I think 0-5V is the normal range. Not a big deal. You just need to follow my directions above and the oxygen sensor is a non issue. 

Edited August 10, 2023 by idosubaru

[el_freddo]

The “secret” to engine swaps in Subarus if not going NA to turbo is to get the correct engine phase (1 or 2) to what you have and AVCS or not. Remove intake manifold from old engine, bolt onto new engine that’s the matching phase (if wrong intake won’t bolt on), ensure the crank and cam wheels match the gear on the old engine coming out of the vehicle. And you’re essentially done. 

Injectors could be too big or small depending on which way you go with the swap in terms of engine size, the ECU will adjust what it can with what’s there AFAIK. 

No need to go swapping wiring or ECUs. You could find there’s some subtle wiring differences in the looms between the two vehicles. 

Cheers 

Bennie

[fuelforwar]

2 hours ago, el_freddo said:

The “secret” to engine swaps in Subarus if not going NA to turbo is to get the correct engine phase (1 or 2) to what you have and AVCS or not. Remove intake manifold from old engine, bolt onto new engine that’s the matching phase (if wrong intake won’t bolt on), ensure the crank and cam wheels match the gear on the old engine coming out of the vehicle. And you’re essentially done. 

Injectors could be too big or small depending on which way you go with the swap in terms of engine size, the ECU will adjust what it can with what’s there AFAIK. 

No need to go swapping wiring or ECUs. You could find there’s some subtle wiring differences in the looms between the two vehicles. 

Cheers 

Bennie

The differences in the looms seems to be my current issue. Both engines are phase 2 non turbo with manual transmissions.

11 hours ago, idosubaru said:

Reinstall the original EJ25 ECU and EJ25 intake manifold and EJ25 oxygen sensor. You did too much work for no reason.

If the engines aren't both from an automatic or both from a manual transmission then swap the EJ25 drivers side cam and crank sprocket onto the EJ22. 

Follow those steps above and you're done.  Have a question....reread the directions above. 

 

More wires just has higher fidelity and I think 0-5V is the normal range. Not a big deal. You just need to follow my directions above and the oxygen sensor is a non issue. 

My main issue with this was I never had a donor ej251. The 2002 impreza was just a roller. I transplanted the complete ej222 out of the 2001 impreza. At this point your saying it would be easier to go out and buy a complete intake manifold with the works, cam gear, and ej251 eco, then it would be to rewire the 02 sensors? That seems like it would be more time and cost consuming then chasing and repinning some wires.

[wtdash]

Try here for the O2 wiring: https://jdmfsm.info/Auto/Japan/Subaru/  

There are more Subaru wiring diagrams posted on other sites too.

No offense, but you stated in the 1st post - that you swapped ECUs, and didn't mention that the EJ251 was no longer avl.,  so that led the USMB to the info above.

 

 

[idosubaru]

9 hours ago, fuelforwar said:

The differences in the looms seems to be my current issue. Both engines are phase 2 non turbo with manual transmissions.

My main issue with this was I never had a donor ej251. The 2002 impreza was just a roller. I transplanted the complete ej222 out of the 2001 impreza. At this point you’re saying it would be easier to go out and buy a complete intake manifold with the works, cam gear, and ej251 eco, then it would be to rewire the 02 sensors? That seems like it would be more time and cost consuming then chasing and repinning some wires.

Nah.  I never said change the engine. Where did you read me say to remove the EJ22 engine?  I didn’t.

Bolt the EJ25 intake manifold onto the EJ22. Leave the EJ22 the original EJ25 ECU will run it just fine  

“Reinstall the original EJ25 ECU and EJ25 intake manifold and EJ25 oxygen sensor.”

Edited August 10, 2023 by idosubaru

[fuelforwar]

5 hours ago, wtdash said:

Try here for the O2 wiring: https://jdmfsm.info/Auto/Japan/Subaru/  

There are more Subaru wiring diagrams posted on other sites too.

No offense, but you stated in the 1st post - that you swapped ECUs, and didn't mention that the EJ251 was no longer avl.,  so that led the USMB to the info above.

 

 

Thanks for the link, I'm going to look through this and hopefully find what I need. Sorry for the confusion on my choice of words with swapping.

 

5 hours ago, idosubaru said:

Nah.  I never said change the engine. Where did you read me say to remove the EJ22 engine?  I didn’t.

Bolt the EJ25 intake manifold onto the EJ22. Leave the EJ22 the original EJ25 ECU will run it just fine  

“Reinstall the original EJ25 ECU and EJ25 intake manifold and EJ25 oxygen sensor.”

I never stated that you told me to change the engine. I'm saying I don't have the ej25 that originally came in the 02 impreza to pull parts from for the ej22. To do it the way you explained I would need to hunt down these parts from a junk yard or buy them new. The 02 impreza was just a car with the drivetrain installed. 

Would it be more efficient to do this or rewire the 02 circuit. I just did a full rebuild on my ej222 before the wreck. I'd like to keep as many new and restored parts as possible before putting used ones on. 

 

[el_freddo]

It might be time then to download the FSM for both vehicles and pull out the ECU wiring diagrams to compare the wiring pin outs for each ECU, find any that are different and rectify if possible. 

And run all the sensors that are factory to the ECU you’re running. It would pay you well to also cross check the wiring for each sensor as there could be wiring changes at the plugs - namely for the O2 sensors off the top of my head as they’re a plug that can have a four plug wire but only three wires in use. If any of these are the wrong way around it will spell trouble. 

Cheers 

Bennie

[fuelforwar]

6 hours ago, el_freddo said:

It might be time then to download the FSM for both vehicles and pull out the ECU wiring diagrams to compare the wiring pin outs for each ECU, find any that are different and rectify if possible. 

And run all the sensors that are factory to the ECU you’re running. It would pay you well to also cross check the wiring for each sensor as there could be wiring changes at the plugs - namely for the O2 sensors off the top of my head as they’re a plug that can have a four plug wire but only three wires in use. If any of these are the wrong way around it will spell trouble. 

Cheers 

Bennie

I appreciate the info. I've been driving the car for the last couple months and everything else seems to be working fine except the 02 sensors, but I'll cross reference where I can to confirm. My gas mileage has been been between 18-20mpg so I'm sure it's due to the fuel trims being off because of the 02 sensors. Where's a good place to find a digital fsm? Basic Google searches on year make and models gave me a mixed bag of results and diagrams.

[idosubaru]

8 hours ago, fuelforwar said:

 

Would it be more efficient to do this or rewire the 02 circuit. I just did a full rebuild on my ej222 before the wreck. I'd like to keep as many new and restored parts as possible before putting used ones on. 

 

 

It's worth looking at the harness diagrams if you don't mind repinning, it just sounds like it could be a rabbit hold if the main engine harness, ECU connector, and oxygen sensor connectors all need repinned. It's worth a look to see, it might just need to be the main engine harness only, or not many pins. Many people don't and sometimes a known solution is better than digging through harnesses towards an unknown end. 

You'll need an FSM which can be gotten online (or pinouts for the necessary connectors - main engine harnesss, ECU, O2 connector) for a Phase II EJ22 and Phase II EJ25. I used to have those digital FSM's but can't find them.  Here's the engines that are all the same if you're looking for pinouts/diagrams online:

Phase II EJ22:  1999-2001 Impreza or 1999 Legacy EJ22

Phase II EJ25: Should be any 2000-2004 Legacy, Forester, Outback, Baja, Impreza, all of those engines are plug and play compatible. 

Or do some combination of visual comparison between both physical connectors and narrowing it down. 

[idosubaru]

Just now, fuelforwar said:

I appreciate the info. I've been driving the car for the last couple months and everything else seems to be working fine except the 02 sensors, but I'll cross reference where I can to confirm. My gas mileage has been been between 18-20mpg so I'm sure it's due to the fuel trims being off because of the 02 sensors. Where's a good place to find a digital fsm? Basic Google searches on year make and models gave me a mixed bag of results and diagrams.

There's isn't a great central source since it varies so much by model/year, I just try to find them linked that doesn't look too suspicious.  I've probably downloaded 20-30 off the internet and never had an issue. 

[fuelforwar]

1 minute ago, idosubaru said:

There's isn't a great central source since it varies so much by model/year, I just try to find them linked that doesn't look too suspicious.  I've probably downloaded 20-30 off the internet and never had an issue. 

Sounds good, I'll just keep digging through fsm's instead of trying to look up individual diagrams just on that circuit. So far I've only been able to find 4 pin diagrams that are a different color then my harness. I wish I dug into this more before I scraped the car. I'd have just chased up the old wiring and replaced it into the new car in the same layout. I even had the whole dash out of the new one to replace the heater core, so that would have been a prime time. That's just the way stuff rolls sometimes tho. Thank you for the info!

[idosubaru]

22 minutes ago, fuelforwar said:

Sounds good, I'll just keep digging through fsm's instead of trying to look up individual diagrams just on that circuit. So far I've only been able to find 4 pin diagrams that are a different color then my harness. I wish I dug into this more before I scraped the car. I'd have just chased up the old wiring and replaced it into the new car in the same layout. I even had the whole dash out of the new one to replace the heater core, so that would have been a prime time. That's just the way stuff rolls sometimes tho. Thank you for the info!

Get an FSM from each of those and compare. I guess start with the ECU and see what’s different. Maybe it’s just the O2 wiring and not the engine.  What you see there will tell you if you need to go to the engine harness or oxygen sensor or not.

Might get away with just pinning the Oxygen sensor to how the ECU wants it and be done. 

[fuelforwar]

37 minutes ago, idosubaru said:

Get an FSM from each of those and compare. I guess start with the ECU and see what’s different. Maybe it’s just the O2 wiring and not the engine.  What you see there will tell you if you need to go to the engine harness or oxygen sensor or not.

Might get away with just pinning the Oxygen sensor to how the ECU wants it and be done. 

That would be great and I'm hoping i get that lucky.

[idosubaru]

4 hours ago, fuelforwar said:

That would be great and I'm hoping i get that lucky.

Don’t know how they all are but I’ve downloaded a few from these links in the past.

Should be able to just put the ECU wiring side by side and compare to start.  
 

https://sl-i.net/FORUM/showthread.php?18087-Subaru-Factory-Service-Manuals-(FSM)-Every-Model-USDM-EU

 

2002 ECU pin outs:

https://www.xcceleration.com/pinouts.htm

Edited August 11, 2023 by idosubaru

[idosubaru]

Be careful with years and models. 

For the 99-01 Impreza 2.2 FSM (a 99 legacy 2.2 should be same), You don’t want a 2.5 or turbo.  Which aren’t common in those years but turbos get a lot of online attention.

For 00-04 FSM you don’t want turbo wiring. 

[heartless]

an excellent resource for FSMs is https://jdmfsm.info/Auto/Japan/Subaru/

[fuelforwar]

So I made a little head way on figuring this out. Tracing all the pins back from the e1 clip to the ecm, there's only one difference between the ej222 and ej251.

The #9 pin on the ej22 bridges with the #6 pin, ties into the c3 pin at the ecm, and the whole branch is fed from the main relay. 

The #9 pin on the ej25 bridges with the #6 pin and is fed directly from the main relay. It doesn't tie in to the c3 pin at all.

On the ej25 loom the c3 pin ties into the tail/illumini nation relay and a lighting switch. 

I'm trying to figure out if I can just tie in a wire between these, or if it would cause a problem with the other system attached. I can't imagine having two positives crossing would be a good idea. Trying to figure out the best way to do this. I drew up a rough sketch to try to illustrate this.

If the voltage is the same and consistent it might be fine, but I'm not sure exactly the function of what the c3 pin does/needs. 

I did pull the sub harness and tested all wires for shorts/breaks. Everything is fine on it. I'm going to test the loom from the e1 plug to the ecm next in case I'm missing anything else.

[fuelforwar]

The only other thing I can think of would be the ej25 o2 sensors just read different than the ej22 sensors. If that's the case I'll need to hunt down the right o2 subharness and order new sensors.

[idosubaru]

Don't know. 

The O2 isn't used by any other system in those older vehiclse (like the AT, there's no dynamic control, cluster, etc) and the rear O2 isn't used for fuel trims until 2005 so that should be really simple.  It just gets scrubbed to see if the CEL needs triggered.  so that should be a simple input, no cross wiring necessary. Of course you'd want it properly powered/grounded/relay/fuse protected and powered at the proper time however Subaru does it.  But it shouldn't need to be shared with any other wiring. 

I'd expect the front to be the same in a 2001 as well - it's a fairly simple O2 and ECU so you should be able to just give it power/ground and pin the input signal to whichever ECU pin needs that signal. 

But I'm just guessing and dislike messing with ECU's/wiring diagrams despite repinning a 2012 Outback connector right now and being a Flight Software Engineer lmao. 

Keep in mind - just in case the wiring turns out to be more complex then initially assumed - I'd still install an EJ25 ECU and oxygen sensor and avoid the wiring. ECU's are available for $25.