1990 ea82 ecu differences

[xbalancex7]

I am wondering if there is a big difference in the ECU in an automatic versus an ECU in a manual tranny.

 

I am trying to understand this neutral switch idea. Ok the only ecu switches from the auto tranny are the inhibitor switch correct? (lets it only start in park/neutral) that can be jumped, rigged, compensated whatever term you want.

 

now the ecu from a manual is supposed to have this mysterious neutral switch for the spfi's. what exactly does it do. I want real numbers......does it modify fuel air mixtures? will it throw codes....the threads say yes, but my mind says no...... will the automatic ecu even have a place for this neutral switch to plug into? does an ecu have to be used from a manual to swap from auto to manual?

 

if the auto ecu does have a place to plug in the neutral switch, why can't I just complete the circuit and make it think there is a switch?.......if all it does is throw codes I'll fake one and hide it somewhere......please someone help me to understand this idea of a neutral switch......i'm so confused. I've read a lot on it and it partially makes sense but something is missing the puzzle is not complete in my mind.

[idosubaru]

EA82 automatic and manual ECU's are interchangeable...of course other things need to be the same, but transmission doesn't matter. if you're doing a transmission swap there is no need to swap ECU's. there's a pin in the harness that "tells" the ECU if it's an auto or manual...if it has the pin it's one, if it doesn't it's the other.

 

any manual switches should only prevent the car from starting if it's in gear or the clutch isn't pushed in. and automatics can't be started unless they are in the proper gear. it's nothing overly complicated about it.

 

if you tell us what you're trying to do (a trans swap i think?) we can be more specific. i think i've seen some EA82's that have differing features...some need the clutch pushed in, some do not, etc. but maybe they were just broke or my memory is bad!

[gravelRX]

You are welcome to borrow my factory service manuals to dig up info. The year is different(87) but the info should be similar enough to get you started.

I would offer to sell them to you but I still have one Subaru to care for and they are very, very handy.

 

Let me know.

 

Jay

[Gloyale]

First, the Clutch switch and the nuetral switch are 2 different things. Clutch switch just disable starting. Nuetral switch tells the ECU when the car is in gear for fuel managment reasons.

 

A manual trans ECU will want to see nuetral switch. Without a neutral switch the car may not idle. Basically, if the neutral switch is not "on" the ECU believes the car to be in gear. During this time it will cut fuel to the engine when throttle is fully closed. This is to save fuel and avoid backfiring. Say... costing down hill in gear. The momentum mean no gas i required so none i used. ONLY if you are fully off the throttle however. So if the ECU doesn't know you are in Neutral, it will cut the fuel when you put the clutch in. BUT.... You can wire the neutral switch signal from a button mounted to the Clutch pedal. If you're car is a Loyale, it will have a clutch lockout button mounted there already that can be used. Or scavenge the plunger type button from a brake pedal with cruise or even the brake switch itself IIRC, and mount it on the clutch pedal. There is already a hole.

 

However......you're car has a Auto ECU. The auto ECU doen't look for that signal. I think, that the problem most associated with the neutral switch is using a D/R without one in a loyale, Or using SPFI on an older 4 or 5spd in an originally carbed car.

 

Doing a Auto to manual swap, you shouldn't need it, you're automatic ECU will not be looking for it.

 

However, that said there are ways to trick the ECU, and grounding or ungrounding one pin can convert one ECU to be the other. Either ECU is capable of being the other. It's all been covered here before.

 

 

But again you don't NEED to. Many have reported doing auto to manual swaps with no problem.

 

You do however need to either permanently defeat the P/N lock out switch, or wire it through a clutch pedal mounted switch like the Loyale manuals

[idosubaru]

does it matter if he's starting with a 3AT or a 4EAT? probably not since the 3AT is a non-computer operated POS!! i have been speaking of the 4EAT - the ECU's across those are interchangeable from auto to manual.

 

helps to know specifics - what you're doing and year, make, model.

[GeneralDisorder]

Ok, lets clear some things up.

 

As far as EA82's go, you cannot "make" a different ECU by changing the harness. They are coded from the factory as either manual or auto and cannot be changed. That goes for the 3AT, and the 5 speed. The 4EAT would be using MPFI anyway as they only came on turbo's. Those could be, and probably are, different.

 

Second, they will run and idle just fine without the neutral switch. In order to turn off the fuel to the engine, the car must be in gear AND the ECU must see a reading from the speed sensor. You could have issue if you put the engine in neutral while coasting with closed throttle. Under very specific and controlled conditions that might result in the engine dieing. Likely as not though the ECU would already have defaulted to running without the neutral switch before you got a chance to try it. It doesn't take long for the ECU to realize that the switch isn't "reporting" and throw a code. This will prevent fuel cut on closed throttle coasting and keep the engine running as a fail safe.

 

You can keep the Auto ECU. You will have to bypass the inhibitor switch in the shifter mechanism. Last one I did went fine but the car did throw codes due to not seeing something from the transmission I think.... maybe kickdown relay, or some gear indicator or something.

 

GD

[idosubaru]

As far as EA82's go, you cannot "make" a different ECU by changing the harness.

you can interchange ECU's though. you can install an ECU from an automatic into a manual. that's what i was getting at, but i wasn't sure why/what exactly he's asking. so i guess it depends what he's doing?

[Gloyale]

 

As far as EA82's go, you cannot "make" a different ECU by changing the harness.

 

Yes, I believe you can. There is a description of how to change the ECU setting to match the vehicle in the FSMs. IIRC in the pre-delivery inspection chapters. I Believe this feature is a "failsafe" provided in case incorrect ECU is installed in vehichle at factory. Can be easily changed by the tech. Unless I am totally misundertanding that chapter. I thought I read about it here as well before.

[xbalancex7]

well thanks guys, I have a vaguely better picture now. I am just gonna put that carbed d/r 5 speed into the auto loyale without changing the ecu and see what happends. worse case scenario I have a cel light on, big whoop. If it runs, it runs in a perfect world I would like to keep my cruz control and not have the cel on, but we will see, time will tell and experience will be my reward.

[idosubaru]

you shouldn't have any problem swapping the trans and keeping the existing ECU. there are a couple things to address but it's not a big deal. cruise should work fine, that operates off the speed sensor in the instrument cluster. i forget what cruise does when you push in the clutch...but yours might do something funny if you go from auto to manual, like rev up? but that's not a big deal.

 

check engine light issues won't be anything to worry about and the car will drive fine with that ECU with very minor work.