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Faulty Wire Or ECU reset? [OBD0]

Idle Air Control Valve Check Engine Light Idle Issue ECU 1991 Subaru Legacy

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11 replies to this topic

#1 Ubatz

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Posted 12 January 2018 - 07:40 PM

I recently replaced an idle air control valve and the check engine light is still on and the idle is still rough. Do I need to reset the ecu? Or do I have a faulty wire? I'm a bit unsure because normally I've never had to reset the ecu.

Edited by Ubatz, 12 January 2018 - 07:41 PM.


#2 Boxer Medic

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Posted 12 January 2018 - 09:46 PM

What is the code? Eg. Circuit fault or position error?

Check power and ground at sensor.

I'm still learning Subaru's, I know the GM linear egr valves must have the battery disconnected for the computer to set the new normal closed valve voltage.

Would not hurt anything and, best of all, its free and easy.

#3 Ubatz

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Posted 12 January 2018 - 09:56 PM

What is the code? Eg. Circuit fault or position error?
Check power and ground at sensor.
I'm still learning Subaru's, I know the GM linear egr valves must have the battery disconnected for the computer to set the new normal closed valve voltage.
Would not hurt anything and, best of all, its free and easy.


It's a code 24. Two long flashes and 4 short ones. the iacv is seperate from the throttle body etc.

#4 Boxer Medic

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Posted 13 January 2018 - 12:07 PM

There are three or four different code 24 definitions based on year of vehicle.

Try disconnecting battery for a minute or two. It *may* fix the problem, if that does not work I would focus on verifying the wiring to the IAC.

Check for power and make sure the ground is less then 100 millivolts with the circuit powered up, key on engine off or running.

There is a chance the air passages are physically restricted also.

What year, model and engine is your car.

#5 Ubatz

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Posted 13 January 2018 - 12:35 PM

There are three or four different code 24 definitions based on year of vehicle.
Try disconnecting battery for a minute or two. It *may* fix the problem, if that does not work I would focus on verifying the wiring to the IAC.
Check for power and make sure the ground is less then 100 millivolts with the circuit powered up, key on engine off or running.
There is a chance the air passages are physically restricted also.
What year, model and engine is your car.


It's a 1991 Legacy with the NA ej22 and an auto transmission.

#6 Boxer Medic

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Posted 13 January 2018 - 02:04 PM

According to http://www.troublecodes.net/subaru/ that code 24 under 1988 and later it says faulty IAC valve or circuit.

Since it is a new IAC that leave's the fault in the electronic circuit.

Here is a list of videos that show how to test IAC circuits:

https://m.youtube.co...E1LTzQSn4mbMjdu

Edited by Boxer Medic, 13 January 2018 - 02:05 PM.


#7 Ubatz

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Posted 13 January 2018 - 06:09 PM

According to http://www.troublecodes.net/subaru/ that code 24 under 1988 and later it says faulty IAC valve or circuit.
Since it is a new IAC that leave's the fault in the electronic circuit.
Here is a list of videos that show how to test IAC circuits:https://m.youtube.co...E1LTzQSn4mbMjdu


Thanks! I kinda get an idea from those. I'm gonna try to let the engine warm up and go for a short drive. and if it doesn't change I'll test power ground and the sensor wire [three wire system]

#8 Boxer Medic

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Posted 13 January 2018 - 06:38 PM

Yeah, its hard to fully grasp initially, for me anyway :) but he does a good job of explaining and showing the how to test and troubleshoot.

Let's see how the drive turns out.

#9 Ubatz

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Posted 13 January 2018 - 08:13 PM

Yeah, its hard to fully grasp initially, for me anyway :) but he does a good job of explaining and showing the how to test and troubleshoot.
Let's see how the drive turns out.


Yeah, I don't have the tools that he has. So I'll use a voltage meter if I have to.

#10 Ubatz

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Posted 13 January 2018 - 10:13 PM

Clearing the code and resetting the ECU again has made it slightly better but the issu still exists so I need to check the wires. I'm hoping it's a bad ground cause that's probably the easiest to fix honestly.

#11 Boxer Medic

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Posted 13 January 2018 - 11:06 PM

Voltmeter works great.

Could be something simple like this...
https://youtu.be/RKzePrS3t_g

#12 wtdash

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Posted 14 January 2018 - 10:47 PM

Take a real close look @ those wires where they go into the IAC connector- the actual harness wires.....on a 27 year 'young' vehicle they may be frayed, cracked, etc.  There's another post on here (or online) showing that issue.

 

This is for a TPS but same idea:

23957d1274635248-tps-settings-p1020078.g







Also tagged with one or more of these keywords: Idle Air Control Valve, Check Engine Light, Idle Issue, ECU, 1991 Subaru Legacy

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