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ECU Pinouts?


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5 replies to this topic

#1 azsubaru

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Posted 21 August 2005 - 02:56 PM

Does anyone know the pinouts on a 91 Loyale ECU? My IAC valve isn't kicking in, and the car won't idle til it warms up.

I cleaned and and then tested the valve by hooking it directly to power. It works that way, but no voltage comes through the wiring harness.

The manual says to disconnect the harness at the ECU and check pin 45, but I don't see numbers on there. Anyone have a diagram or any ideas?

Thanks!

#2 hooziewhatsit

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Posted 22 August 2005 - 12:28 AM

http://www.finleyweb...ault.asp?id=142

In part 2 of the EA82 service manual, it has pinouts for an SPFI wagon. It also has troubleshooting guides for most of the electrical stuff. Even though your's is a '91, it should be the same thing.

Let me know what you find out with your IAC valve. I need to go through the guide for an '87 wagon I have currently.

#3 PoorManzImpreza

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Posted 22 August 2005 - 06:06 PM

iac shares power from fuel pump relay..usually a nice sky blue wire..

#4 azsubaru

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Posted 25 August 2005 - 03:16 PM

Followup - Thanks for the information, guys, it helped a lot.

The manual link was great! I used page 67 of the document for a reference. It has a diagram and a troubleshooting flowchart. You can actually print that out and then ignore all the stuff I've put below - it's redundant.

In hopes that it may help someone, here's the story:

My problem is that the IAC valve in my 91 Loyale doesn't kick in, so idle is a problem when the car is cold. I checked the valve by hooking a lead to the white wire at the valve connector and connecting the other end to ground. The valve worked fine - it closed and the idle went up just like it should. So that means the valve is getting voltage, and works as it should when bypassing the ECU and associated wiring. This is a good quick and easy check that eliminated everything from the power side, up to and including the valve itself as being problems.

With help from the page from the manual, here's what I found:

The IAC valve is always hot when the key is on, so you should get 10 volts or more on the black and white wire at the valve anytime the key is switched on. The ECU simply goes low on pin 45 for the first minute after the key is on, which completes the circuit for the valve, effectively adding the ground. After a minute, pin 45 goes inactive, releasing the IAC valve. Pretty simple.

Since the valve is always hot, you can disconnect the yellow connector at the ECU, hook up a multimeter to it (the connector), switch the ignition on, and you should read 10 or more volts coming through the green and red wire on pin 45. The green and red wire goes directly out to the white wire at the valve.

Luckily pin 45 is on the yellow connector at the ECU that's closest to you when you look up at it - in other words, it's the closest connector to the steering wheel, so it's easy to get to. The plug for pin 45 is right in the middle, on the bottom of that connector - you'll see the green/red wire. So stick a meter lead in that slot, the other lead on ground, and see if you have voltage there. If you have voltage, you've pretty much proven that the circuit works all the way to the ECU. If not, and the valve worked earlier, you have a problem in the wiring between the valve and the ECU.

Turn the key off and plug the connector back in. Then stick the multimeter lead in the back of the connector (with the other lead still on ground), then turn the key on. It's a bit of a pain to get the lead in there. I used a piece of stiff wire and alligator leads to get the connection. The meter should read low - 1 volt or so - for about the first minute and then go high. This is the ECU doing it's job.

When I checked mine, I had about 12 volts voltage on the wire all the time at the ECU, so it appears that my ECU has gone on to the big Loyale in the sky. Now I have to find one at a reasonable price and see if it corrects the problem.

#5 hooziewhatsit

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Posted 25 August 2005 - 05:07 PM

Followup - Thanks for the information, guys, it helped a lot.

When I checked mine, I had about 12 volts voltage on the wire all the time at the ECU, so it appears that my ECU has gone on to the big Loyale in the sky. Now I have to find one at a reasonable price and see if it corrects the problem.


Thanks for the update. I have yet to follow this guide on my 87 with the IAC code.

I suspect that the problem is something in the ECU as well. That being said, I *may* be able to repair it :) This is probably similar to what happened to Citrusshark and his injector problem. I also suspect this problem with my 88 GL and the EGR light.

I'll have to 'examine' the ECU from one of my cars today to figure out whether or not this fix could be made.

If you do find another ECU for cheap, I would be interested in acquiring yours to do some testing, if that's alright.

-Dave

#6 azsubaru

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Posted 25 August 2005 - 06:59 PM

If you do find another ECU for cheap, I would be interested in acquiring yours to do some testing, if that's alright.
-Dave


No problem - I'll be happy to send it to you once I get a replacement. I've been playing with the idea of putting in a manual switch to handle this for the time being. It would be sort of like the manual choke that was on my old Triumph TR3, except electronic instead of mechanical.




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