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Frank van Rouendal

3 pin ISC

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Hi, I have a G1V14 on a Subaru 3 liter engine. Engine is running fine now (see earlier discussion "Syn/Cyl Ratio"), but the ISC does not react to the ECU. ISC is 3-pin, see picture. The part number is 22650AA21B, a.k.a. 22650AA211. I tried +12V on centre pin and ISC 1/2 control on the other pins, but no result. Any idea about the correct pin arrangement? Frank van Rouendal

post-2752-143621570291_thumb.jpg

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Hi , Frank I have had simmalar issues with one of my units ,But it turned out my AFR were way off & the ISC couldnt compensate for the error in tuning, Also did you refrence the "documentaion" area, I saw what your looking for in either the "tecnical notes" or tech drawings,they do list CAS wiring as well as the CKS wiring for both 3 & 2 wire sensors Jay

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Hello Jason, Thanks for your information. I had checked the tech. drawings before, but these give no clue about exact pin arrangement. I hope Link knows this. I doubt that my AFR is wrong, as the engine runs fine, only doesn't idle. Besides, I will check movement of ISC during running, by connecting a separate ISC to the loom, and changing idle speed setting in the program. Hope this will give me more understanding of what is wrong. With regards, Frank van Rouendal

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Hi Frank.

Have you seen this image, or is this the one you're talking about? http://www.linkecu.com/support/documentation/technical-drawings/A01

Ahhh... After a discussion here, we think your one is the later ISC.  Here is a pic of a scanned image we found that may help.  We'll try and get this up on the website too.

http://i903.photobucket.com/albums/ac236/linkelectro/subaru_ISC.jpg

 

Jurgen

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Hello Jurgen, Thanks for the info. My ISC looks like the last picture, with 3-pins. I have some trouble understanding the pin connections, as I have TWO control wires coming from the ECU: ISC-O and ISC-C. This contradicts the pin assignment in the picture, showing 12 V+, ground and ONE control wire. In the meantime, I did a test with the engine running and setting the speed by throttle. With the ISC connected to the ECU and going through the idle speed range, I noticed that the ISC valve did make some small movements. So I asume that the basic connection is OK, maybe I need to switch ISC-O and ISC-C connections. Now I will study all ISC setting details in the manual, and try to set my ECU correctly. Any advice from you in this matter is welcome. With regards, Frank van Rouendal

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Hi Frank,

If you want to confirm on a 3 wire 'push-pull'  ISC which pins are ISC-O and ISC-C. With just the 12v connected, when you ground the ISC-C pin, the engine should stall unless you have air coming into the manifold elsewhere. And when you ground the other pin, ISC-O, the engine should rev as high as the idle can let it.

What frequency are you running the ISC at?

-Cameron

 

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Hello Cameron, Thanks for your advice. I did following tests: - Started engine with ISC connected to ECU and IS-setting 1250 rpm: engine stalls unless throttle is opened. - Started engine with ISC disconnected: engine idles at approx. 1500 rpm with throttle closed. - With engine running, throttle closed and +12 V connected to middle pin of ISC, grounded right pin: engine slows down temporarily to approx. 1000 rpm, returns to 1500 rpm after 0.5 sec. - With engine running, throttle closed and +12 V connected to middle pin of ISC, grounded left pin: engine remains at 1500 rpm. - With engine running and throttle closed, connected ISC to ECU again: engine stalls. This mystifies me quite a bit. What would you make of this? I do not understand what you mean by the frequency I am running the ISC at. Cannot find this in the manual. Please explain. Hope you know the answers. With regards, Frank van Rouendal

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Hi Frank,

From those results you appear to not have a push-pull type. The ver7 solenoid http://i903.photobucket.com/albums/ac236/linkelectro/subaru_ISC.jpg has some 'smarts' inside it and you should just be able to wire it as per that picture, the 'To ECU' pin goes to ISC-C and ISC-O is not connected to anything.

-Cameron

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Hi Cameron, Thanks for your advice. Connected the ISC as indicated in the picture, but still no results. PCLink screen correctly indicates "increasing idle" or "decreasing idle" depending on IS-setting and actual RPM, but no reaction from ISC. 1. Tested wiring between ECU and ISC connector, both ISC-O and ISC-C are OK. 2. Checked for voltage between ISC control wires and earth during idling, this stays zero. 3. Checked for variation in resistance between ISC control wires and earth during idling, this stays at infinite. 4. Tried to catch signals from ISC control wires on the scope during idling, but not more than 20 mV (constant) through all idling phases. Some noise, showing as spikes. At all tests throttle position was 10 = closed. Please indicate what type and level of signal I should read on ISC control wire(s), so I can check whether ECU is not sending or ISC is not receiving. Engine idles fine on mechanical adjustment of ISC actuator on ISC body, but this depends on engine temperature, and is not controlled by ECU. Hope you know how to solve this. With regards, Frank van Rouendal

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Hi Frank,

I'm not sure why you're mentioning the ISC-O wire as that should not be used.

I think the problem you are having is that the ISC-C just provides a ground, and this won't give you the square-wave signal that the ISC may be looking for. To counter this you can wire a 1k ohm resister to 'pull-up' the voltage when the ECU is not grounding the pin. This will go between the ISC-C wire and 12V and can be done at the ISC end or the ECU end. Once this is applied you should then see a 12V square wave signal and the duty cycle (time on vs time between pulses) should increase and decrease with idle control.

Good luck

-Cameron

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Hi Cameron, Thanks for the info. Installed a 1 kOhm resistor between ISC-C and 12V at ISC side, and put the signal on the scope (screen-101.jpg). No result. Added 1 kOhm to the first, then another 1 kOhm, reducing the resitance to 500 Ohm / 330 Ohm. Same picture on the scope, no result. Took all resistors out, same picture, no results. Incidently, the 12V supply to ISC shows the same kind of picture on the scope (screen-104.jpg). I see no useful 12V - 0V square wave signal at ISC-C. Hope you can understand what the problem is. With regards, Frank van Rouendal

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Hi Frank

A bit of a long shot but does the ECU have a stepper motor control board fitted? This will be a sub-board in side the ecu with either 4t stepper or 6t stepper printed on it.

If it has either remove it and then see if you get a good signal.

Simon

 

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Thanks for the picture

From that I can confirm the stepper control board is not fitted. Down side is that it is not the cause of your ISC not working.

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Hi Frank,

I have just tried on the bench and the ISC-C should output a square wave with nothing connected. It will be between 12V and Ground at 180Hz. The duty cycle will depend on the values you have set for Idle hot and idle cold. It will not output a signal unless you have an RPM signal and your throttle is closed.

If you don't have this possibilities could be:

You're checking the wrong wire.

The circuit could be faulty

Your TPS is not setup correctly

Your idle settings are wrong.

 

Good Luck

-Cameron

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Hi Cameron, Thanks for your info. and advice. I see a signal as per attached picture. Roughly 40 Hz, between 14.0 and 14.5 Volt. This does not bring the ISC into action. - Wires are OK (measuring ISC-C against ground, with 1 kOhm resistor between 12 Volt and ISC-C). - TPS set-up is OK (reads 10 during idling, 100 at full throttle). - Idle settings 60 hot, 70 cold. Engine idles at 900-1000 rpm after warming up (mechanically set by means of adjusting ISC actuator on ISC valve body). At the moment I think that the ECU does not generate the correct signal for this type of ISC. But as the car is scheduled for rolling road dynamometer tests soon, I will leave it as it is. With regards, Frank van Rouendal

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