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ECU still thinks its an automatic (5MT swap)


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9 replies to this topic

#1 Ibreakstuff

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Posted 05 January 2013 - 05:44 PM

So i've been driving my 1990 loyale with a 5mt swap (fwd) for a couple years now. Its smog time again (california); so instead of taking the dash apart again to hack the check engine light again I am looking to fix the issue properly..

I am wondering, what exactly tells the ECU that the car is auto/manual? Is there a pin that needs to be grounded or jumped? I've scoured over hundreds of forum posts and the manuals I have access to and cannot find the exact solution.

Notes:
-Car was originally FWD 3AT
-Currently swapped 5MT fwd
-Currently using an ECU from a 5MT loyale (still thinks its automatic)
-Only showing ECU codes 08 (ca automatic) and 51 (neutral switch)

I'm tempted to do a full wiring swap, as I already have the bulkhead harness from a 5mt loyale.. Which would give me the correct transmission connectors. But swapping the body harness doesn't sound like much fun.

Anyone familiar with this? Most people seem to just jump the inhibitor switch and call it done.

#2 jono

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Posted 05 January 2013 - 07:43 PM

Can't see that Subaru would change things that much between the years and models. If it helps, a few years earlier the EA82 L Series ECU with three plugs 85 and 86 models it was a simple ground or not grounded pin on the ECU.

What is it doing that makes you aware it thinks it is still an auto?

#3 Ibreakstuff

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Posted 05 January 2013 - 08:40 PM

Can't see that Subaru would change things that much between the years and models. If it helps, a few years earlier the EA82 L Series ECU with three plugs 85 and 86 models it was a simple ground or not grounded pin on the ECU.

What is it doing that makes you aware it thinks it is still an auto?


I wish I could figure out which pin that would be, looking at the schematics I can't seem to find it.

It definitely still thinks its auto tho per the 08 identification code, would show code 07 if it was cali manual (which is what the ecu came from).

In "auto" mode the neutral switch is on to start, then off when in gear. In manual mode it is reversed, so currently I am not able to wire in the neutral switch directly from the transmission. Also in auto mode, if the switch is continuously on it gives a CEL and code 51. I guess I could just wire in a toggle switch to the inhibitor for starting only, this to prevent it from popping the 51 code (at least to smog).

The only adverse effects that I have noticed day to day are a higher than normal idle and lifting off throttle too fast will try to throw my face into the steering wheel. I believe both of these would be resolved with the correct fueling from the ECU with a working neutral switch.

Maybe my understanding of how it works is skewed, please someone correct me if I an wrong.

#4 86BRATMAN

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Posted 05 January 2013 - 09:34 PM

do you still have the tcu plugged in, or does that even apply to the 3at

#5 TomRhere

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Posted 06 January 2013 - 09:53 AM

Been digging thru diagrams myself, trying to clear some errant codes.

Not sure if it's what you'll need but got a few wires for you to check on the connection to the ECU. This is on the middle connector plug.

Looking at it from the wiring side, catch-clip up.

Pin #1 top row left side, Blue/green wire, AT kick-down control.
Pin #13 bottom row 4th position from left side, Yellow/red wire, AT inhibitor switch.

Neither of those wires are present in the connector on a Manual trans car. Or atleast they're not on my '88 GL Wagon or the '92 Loyale Wagon, both are Manuals.

#6 ivans imports

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Posted 06 January 2013 - 11:28 AM

the front car wire harnes is a bugger to change but not impossibble takes about 3 hours and have to pull bumper and both front fenders and dash and i whould change the whole front harness leave the rear harness alone

#7 Ibreakstuff

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Posted 06 January 2013 - 11:33 AM

do you still have the tcu plugged in, or does that even apply to the 3at


No TCU on the 3at

Been digging thru diagrams myself, trying to clear some errant codes.

Not sure if it's what you'll need but got a few wires for you to check on the connection to the ECU. This is on the middle connector plug.

Looking at it from the wiring side, catch-clip up.

Pin #1 top row left side, Blue/green wire, AT kick-down control.
Pin #13 bottom row 4th position from left side, Yellow/red wire, AT inhibitor switch.

Neither of those wires are present in the connector on a Manual trans car. Or atleast they're not on my '88 GL Wagon or the '92 Loyale Wagon, both are Manuals.


Thanks for the lead Tom, the kickdown control seems like a good suspect. I'll test those pins today.

#8 Wayback

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Posted 06 January 2013 - 02:38 PM

For an AT SPFI, ECU pin 32 is grounded. To make it an MT, you need to cut that wire. It's a black/red on the largest of the 3 ECU connectors, second from one end between a brown and a light green.

#9 Caboobaroo

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Posted 06 January 2013 - 02:54 PM

Nw ant to do it the easy way? I believe the 6 pin connector that plugged into the original automatic shifter needs to have a jumper wire installed. Out of the 6 wires, find the two largest and put a wire to connect them. I then wrapped the jumper wire and the connector with electrical tape to keep the jumper secured. This was on my '87 but I don't see it being that much different. Wires should be Black/Yellow stripe and Black/Red stripe.

#10 Ibreakstuff

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Posted 07 January 2013 - 02:59 AM

the front car wire harnes is a bugger to change but not impossibble takes about 3 hours and have to pull bumper and both front fenders and dash and i whould change the whole front harness leave the rear harness alone


Its a lot easier if you just pull the headlights, then you don't have to pull the bumper/fenders. The hardest part to reach being the plastic ties on the lower radiator support. I got away without pulling the dash too, but the driver side fender liner does have to come out. And installing it would probably be a hell of a lot harder!

I have learned so much in the last couple years from pick-n-pull lol.

Nw ant to do it the easy way? I believe the 6 pin connector that plugged into the original automatic shifter needs to have a jumper wire installed. Out of the 6 wires, find the two largest and put a wire to connect them. I then wrapped the jumper wire and the connector with electrical tape to keep the jumper secured. This was on my '87 but I don't see it being that much different. Wires should be Black/Yellow stripe and Black/Red stripe.


This is what I did and has been running for the past year or 2, the problem is that it pops a CEL (code 51). And runs a bit weird. The CEL and high idle keeps me from passing smog, tho there are ways to get around that.

For an AT SPFI, ECU pin 32 is grounded. To make it an MT, you need to cut that wire. It's a black/red on the largest of the 3 ECU connectors, second from one end between a brown and a light green.


This is what I was looking for!!! Thank you so much, I'll give this a try in the AM and post back with confirmation.

Now that I take a second look at the wiring diagram.. I do see that pins 32, 1, 46, and 13 are designated for AT. I feel dumb that I did not see these before.




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