ECU ID codes?

[Fairtax4me]

Now my search is on for an ECU. I notice there appear to be quite a few number/letter codes (2N, 5P, 3Q, etc.) for the ECU's.

I know the pinouts are different between years around 96, so I need a 96 ECU, but the big question is...

Is there any way to decipher the 2 digit codes to know exactly what year car the ECU came out of, and is it EGR or non-EGR? Or some other random difference that I may not know about?

 

I didn't note the number on mine when I had the cover off earlier, but will get it at some point this week, and will probably post a want ad for it here since I don't exactly trust eBay for something like this.

[johnceggleston]

attached is a link for the ECU for the 90s, ej22, wagon, auto trans.

 

the dates listed with the part numbers are build dates. if these are like most others there is a fair amount of over lap in the dates. (FYI the ecu is located in the ''engine electronic'' section, ''relay & sensor''. )

 

http://opposedforces.com/parts/legacy/us_b11/type_25/engine_electronic/relay_and_sensor_engine/

 

same below for manual trans :

 

http://opposedforces.com/parts/legacy/us_b11/type_24/engine_electronic/relay_and_sensor_engine/

 

it appears that the ECUs are used for both the auto and manual trans cars. it is my understanding that the wiring harness, not the ECU, is what determines if it is auto or manual trans designated.

 

i would assume the same is true for the EGR, but i do not know. and if that is the case, i would have thought someone would have found the correct pin to ground out. but i'm pretty sure the ECU is not trans specific in 96. if you click on the part number in the link above and then the ''usage info'' it will list the cars that use the ECU.

 

and i have swapped a 96 'L' ECU into a 97 GT with out any headache. (if you are not in a hurry, the 96 ECU is available. i just have to locate the 97GT ecu and swap it back in. let me know if interested)

 

but i cannot say the same for a 97obw ecu in a 98obw. the car will run fine but you will have ''ghost'' trouble codes. there will be a CEL but no real trouble. just an ECU looking for info on a pin that it is not receiving.

Edited October 24, 2012 by johnceggleston

[czny]

If its any help I just pulled a 22611ac431 ECU, with 7P on center from a 96 Lego OB, EJ22, 5mt, no egr, Calif. OBD2.

[Fairtax4me]

it is my understanding that the wiring harness, not the ECU, is what determines if it is auto or manual trans designated.

This is my understanding as well. I have tried to find some sort of info that this is true for the EGR as well but have no luck when searching through various wire diagrams and ECU I/O diagrams. The MT/AT identifier is clearly labeled on I/O charts, at least for the earlier models.

 

but i cannot say the same for a 97obw ecu in a 98obw. the car will run fine but you will have ''ghost'' trouble codes. there will be a CEL but no real trouble. just an ECU looking for info on a pin that it is not receiving.

 

Maybe 96 and 97 are the same. I was thinking 97-98 were same.

I do know that 95 and 96 are different. On 96 pin 29 is one of the crank sensor signal wires, on 95 pin 29 is for the ECT sensor signal. That ain't gonna work too good.

[Fairtax4me]

Appears I have:

 

Ebay has one for $110. Looks like it was in a fire, then drowned.

http://www.ebay.com/itm/22611-AC910-ECM-ECU-COMPUTER-95-96-97-98-SUBARU-LEGACY-22611AC910-/261039360338?pt=Motors_Car_Truck_Parts_Accessories&hash=item3cc7288952&vxp=mtr

 

I wouldn't pay that much for one anyway. My wallet is too vacant as it is, unless I can find one for like $20 I'll probably just let it ride for another 3 years. :-p

 

The differences (im sure minor) between a 9M, and a 2N, and a 3C, and whatever else, still interests me. What I can't figure is, why so many? :-p

[czny]

Roaming around a pick your part yard found a 96 ej25, auto Lego OB. Pulled up the carpet, found ECU was 22611ac341, 1Q!

Like you say, why so many???

[Fairtax4me]

Finally found mine listed on opposedforces website.

http://opposedforces.com/parts/info/22611AC910/

 

Depending on model I can get one from certain 2.2 engine cars made between January 1996, and May 1998.

 

Automagic or manual trans does not appear to matter. The only real difference I can see is that it doesn't come from a 2.5, and that it has the same evap system, which is a consideration I had not thought of before, but makes sense.

[johnceggleston]

the link shows that it was used in the jan 96 - may 96 outback step roof manual trans ej22 car. i have seen it posted several times there is no EGR on that car. and there is usually no EGR on the mnaual trans ej22 96 - 98.

 

so the ECU does not care if the car has EGR. it has to be the wiring harness.

 

also, your link shows your ECU was used in the 96 ej22 outback manual trans car. but when you look that car specs up it does not list your part number. odd.

but it appears any of those part numbers listed in the link are interchangeable for the listed cars.

 

that is how the auto trans id numbers work out. you look up the auto trans for the 97 outback ej25 and it will show the different part numbers for each year, 96 - 98/9 with the corresponding trans ''id'' numbers. if you look at the usage info for any one part number, any one trans id number, it will show that it was used in all 4 years, 96 - 98 and a few early 99s.

 

so you need an ECU from a late 96 or 97 - 98 ej22 car. lots to pick from.

Edited October 27, 2012 by johnceggleston

[Fairtax4me]

also, your link shows your ECU was used in the 96 ej22 outback manual trans car.

It does show it. http://opposedforces.com/parts/legacy/us_b11/type_46/engine_electronic/relay_and_sensor_engine/

 

Also still not sure about the EGR, unless we assume that if a car had an automatic transmission that it MUST then have EGR. I know some auto Ej22s in that era do have EGR, but do ALL of them have it?

My car is non-EGR, so it makes sense that the non-EGR 96 Outback MT ECU could be the same.

 

To thicken the plot a bit more... one of the other part numbers listed (22611AD55A) says it was used as far back as march 94 (which would make it an early 95 MY vehicle). That makes no sense if according to wire diagrams the pinout is different on 95 MY ECU.

 

But, it looks promising that I can use an ECU from a 96 - 98 Ej22 car. Certainly widens the list of possible donors.

[johnceggleston]

Also still not sure about the EGR, unless we assume that if a car had an automatic transmission that it MUST then have EGR. I know some auto Ej22s in that era do have EGR, but do ALL of them have it?

 

i know there is at least one member who has direct evidence that not all auto trans cars had EGR and that not all manual cars did not have EGR.

 

but i can not find any evidence on http://opposedforces.com to show the same. the only cars listed that show an ''egr pipe'', (an integral part of the EGR system,) are the auto trans cars. none of the manual trans cars show an EGR pipe as a part number.

 

so for the sake of discussion, and based on the opposed forces web site, 95 - 98 ej22 cars with auto trans have EGR and NONE of the cars with manual trans had EGR.

 

this is not a guarantee, this is simply a trend. sometimes reality is different than the plan.

[Fairtax4me]

Grabbed 2 different Ecus from the junkyard. One out of a 96 Outback. 2.5 AT, EGR. Made it two days on that one and got three codes for AT diagnostic circuit, Evap incorrect purge flow, and EGR circuit.

P1702, P0441, and P0403.

 

Second ECU is out of a 97 L. 2.2 AT, engine gone, but assume it had EGR.

Two days and no codes on this one yet, but it hasn't set the IM monitors yet. Once I get it to greenlight the monitors I'll be happy.

 

Seems strange that the one out of the OB would set the AT diag code though.

Other strangeness: Cold start it would rev to about 2000 rpm for 3 seconds, then it would quickly drop to 1000 rpm and would stay there seemingly indefinitely. It would idle down to 700 on occasion if the car sat still for long enough. When coming to a stop it would hold idle at about 1200, and come down to 1000 once stopped.

 

The one out of the 97 seems to work properly. Get good readings from all sensors and idle sits steady at 700 rpm as it should. Even feels like a little bit of power is back. Fingers crossed it'll set the IM monitors and stay happy.

[idosubaru]

what were you trying to do? you had a working ECU but were trying to replace it - due to check engine codes? i've done a bunch of ECU swapping in mine so i'm curious.

 

i don't think the part numbers mean much. they seem to change as protocol, yearly, batches, or something. even in 80's Subarus there's gobs of part numbers for the exact same ECU's and vehicles - like XT6's. i've got boxes of them and they may have all different numbers but they're all the same for non-odd ball vehicles (like the 1987 change over year stuffs and 1995 like you mentioned).

 

i've used at least 3 different ECU's into my 1996 LSi EJ18 FWD automatic (originally EJ25 AWD). noticed no differences between them and got the same codes. curious why you're swapping yours. ECU's i've ran are the original EJ25, EJ22, and a non-EGR vehicle (forget which motor) that's currently in it.

 

I deleted the EGR as soon as I got the car when i installed the EJ18. i even cut the EGR wires at the ECU and installed a non-EGR ECU....and ***still*** got EGR code? luckily it doesn't matter in WV, they don't do emissions or look at the check engine light so I've just left it.

 

but this suggests the ECU's between EGR and non-EGR are interchangeable.

 

there is no rhyme or reason to automatics. after 1995 it's a crap shoot. in my area it seems most of the auto's had EGR's, but not all.

 

manuals i'm unsure of.

[Fairtax4me]

Old ECU showed a constant reading of 0"Hg from the MAP sensor. Kept getting DTC P0106. After many hours spent diagnosing determined the cause must be the ECU since all three sensors I have test fine on the bench, but when hooked up on the car all defaulted to something like 0.9-1.1v output signal that would not change with changes in vacuum. ECU thought the engine was pulling 30" of vacuum at all times. Details in my MAP sensor re-visit thread.

 

New ECU hooked up, sensor output (at sensor) is within FSM spec. ECU reports 8.5"Hg at idle, unhook the vacuum hose on the MAP and get 29.2"Hg (atmospheric pressure). Subtract 29.2 from 8.5 means the ECU is seeing -20.7"Hg (vacuum) at idle, roughly within spec. Change in throttle position produces an immediate change in MAP reading on the scanner.

[johnceggleston]

sounds like you found a winner. maybe the ECU will ''learn'' and the car will run / idle a little better.

 

or did you mess with anything while the bad ecu was giving you headaches that might have affected the idle??

 

just a thought.

[idosubaru]

no kidding, wow! did you mean "MAF" or "MAP"? i thought these 96's were MAF sensor based?

 

anyway, how did the car drive? any performance difference?

 

that is really strange stuff you encountered.

[ivans imports]

have many ecus of the 96-99 era have done some interchanging the 2.5d outbacks did not like the 2.2 legacy ecu gave me a high idle on startup but no egr codes but had to put the 2.5 ecu back in to get it to run right.

[Fairtax4me]

Never messed with anything other than the MAP sensor. Swapped some other sensors (knock, maf, ect) here and there while troubleshooting, but I never tied any real trouble back specifically to the MAP problem. (Or any other sensor for that matter.) I suspected some running issues might have been related but they would come and go at random. There was an issue that only popped up when it was really hot outside (like 90+). Have to wait til summer to find out if that one's gone.

 

 

I know there are some oddball years out there that have either MAP or MAF. Mine has both.

 

I did take the old ECU apart. Didn't find anything blown up or obviously broken.

[adebowski]

I know this thread is a bit old but I've run into a conundrum.  I have a 98 Legacy Outback that passes emissions just fine and a 99 Legacy Outback I just got that won't show a ready status for 3 IM sensors (catalytic, evap, and erg).  I don't know much about the 99s history and want to rule out the possibility that the ECU that is in there was pulled from a 96 which I know can forever show those codes as NOT READY.    The question is, can I just put the ECU from my 98 into the 99 and see if the codes will go to ready status or will I have to have it get reprogrammed at the dealership.  I am basically trying to exclude problems before I go swapping more parts.

 

Thanks for the help.

[Fairtax4me]

IIRC Those are the three monitors have to have a very specific set of circumstances completed in a certain order before they will set Ready.

 

Try the method in the link from this thread: http://www.ultimatesubaru.org/forum/topic/134825-subaru-tsb-how-to-set-your-im-monitors-for-emissions-testing/

 

That should get the monitors set. Once set they should stay set. If they don't stay set then there is an issue with the ECU.

[johnceggleston]

if the wiring in the 99 is the same as the wiring in the 98 (no changes made that year?) then yes you can swap the ecu and it will run the car with out codes.

but that does not guarantee that the monitors will set up.

plus when you pull the ecu and remove power it will reset, clear codes etc.

you'll be starting from scratch.

 

but even if they made a minor change that year, it should not keep the ECU from running the car.

it may throw a phantom code, saying you have an issue when you do not.

i had that hapen when i put a 97 obw  ECU in a 98 obw.

i got codes for incorrect purge flow and a traction control issue.

my car did not have any traction control equipment so no possibility of that code being valid.

and once i put in a 98 obw ECU both codes went away.

 

i feel like i remember one case where the trickle power wire to the ECU that kept it ''alive'' when you turn the car off failed, and the ECU would reset when the key was off.

i think i remember that, but i don't know what year had the problem.

 

worst case if you swap the ecu is it does not help and you have to swap back.

Edited August 27, 2013 by johnceggleston