ISC/IAC testing questions and issues (Merged)

[98gsxturbo]

Hey guys well i just got done testing my ISC to see if it was messed up or not. I looked up some instructions on the net and followed them, and i got the following readings on my ISC in Ohms. This is a basic diagram of the pins in the ISC that I measured..

1 2 3
| | |
| | |
4 5 6

Pins 1 & 2 = 27.4 Ohms
Pins 2 & 3 = 27.5 Ohms
Pins 4 & 5 = 27.0 Ohms
Pins 5 & 6 = 27.4 Ohms

Where my instructions were it says that acceptable readings were anywhere between 28 and 33 Ohms. I'm a bit out of that range. Should I consider my ISC shot and replace it? If any of you guys out there with a shop manual can look this up to verify it that would be most helpful. thanks!

 

[TURFNNSURF]

Guys, I know the VFAQ site talks about it. But I have just heard a different version: "You check the resistance of the isc motor coil from the plug that goes into the isc. Then you apply 6v to the motor itself. That's how you test the isc. "

The question is: Should I check the resistance on the plug that goes to the ISC or the ISC motor itself??

Test you ISC just like it is described in this link ~~~~> http://dmtalon.v8eaters.com/ISC.html

Don't test the pigtail to the ECU until you test the ISC first. If the ISC tests OK then check the pigtail to see if the circutry in your ECU id faulty.

 

[cevic]

The link that you provide is exactly same as the one in VFAQ.

Ok, when we say ISC, are we referring to the stepper motor or the system (the web-site sometime says ISC and sometime says ISC motor)? Are we checking the the resistance at the pins on the back of the stepper motor or the plug connector?

The story: I just brought a ISC motor from some guy. I test the ISC motor following the procedure in this website: http://dmtalon.v8eaters.com/ISC.html. I got ~29.3 ohms between pin 1-2, 2-3, and 4-5 but only 1 ohm on 5-6. I talked to the guy and he told me the way that I test was wrong and refused to ship me another unit.

 

[TURFNNSURF]

I got ~29.3 ohms between pin 1-2, 2-3, and 4-5 but only 1 ohm on 5-6. I talked to the guy and he told me the way that I test was wrong and refused to ship me another unit.

Well, that's a real bummer, you got robbed by that guy then. I hope he wasn't a member here on tuners. I just tested three ISC's I have here in my shop and they all test good 31ohms @ 70+ degrees between pins 1-2, 2-3, 4-5 and 5-6.
If you don't have a junkyard near you where you can pull the part yourself then I'm afraid you'll have to buy another one to use.

Also I was wrong about testing the pigtail to the ECU. The other part of testing the ISC motors is to use a 6volt battery to make the motors twitch when voltage is applied. If they don't move they are shot.

 

[Boothman]

Hi folks.

I'm glad that I've found this forum and a lot of great informations.
Since over five years I'm driving my Eclipse NT (only in summer) and from year to year, I love my car more. I guess most of you also do so...

I'm not a car professional, but since nearly ten years I'm screwing on engine powered vehicles - so I could collect a bit knowledge.

I have a problem, I can't solve... it's the ISC.
I've already tested the coil resistance according to the manual. Every tested coil hat about 27.x Ohms at about 60°F. The range in the manual is 28-33Ohms. But I guess, my value might be ok...?
After this test I've replugged the cars connector the ISC (I didn't reinstall it to the engine) and somebody switched the egnition on and off. The result is, that the ISC did only make short vibrations. The pin did not move forward or backward - so it seems, it's not working properly.
I've read the thread about rebuilding an ISC, but there were only some Informations for what to to if the coils are damaged.

My question is: What might be wrong with my ISC and is there something I can do to make it move again until I order that expencove thing..

I hope, somebody of you can help me and answere my question...

Greetings,
Boothman

 

[90_LASER_RS_420]

when i am testing my isc does the key have to be turned over at all, because i've tested both the power supply and the connectors and im only getting 3-8 ohms???

 

[steve]

If your measuring the coil resistance of the ISC then you can do it with the ISC out of the car.
Exactly what are you trying to do?

Steve

 

[90_LASER_RS_420]

I'm trying to find the ohms, because in a previous thread it said 28-33 ohms on 1-2, 2-3, 4-5, 5-6, on the prong things. I know, I know, it sounds stupid please don't comment on my terminology. I was just wondering to get these ohms does the car have to be on acc. or no power at all?

 

[steve]

I was just wandering to get these ohms does the car have to be on acc. or no power at all?

While it might not be obvious that you have to disconnect the harness from the ISC to measure the resistance of the coils in the ISC. That would mean that it doesn't matter what you did with the ignition switch because the ISC is disconnected from the car for testing.

You would use a whole different set of test is you were trying to measure the car harness rather than the ISC.

Steve

 

[Auto RS T]

He doesn't have the pins because he doesn't have a 2 bolt ISC with pins, it has an extension harness.

Is the resistance test still the same for a 90?

I tried searching for a 90 ISC test but couldn't find anything that specifically stated the 91-94 test were the same, and my 90 manual is at the shop.

 

[90_LASER_RS_420]

ok, thanks, my multimeter must be screwed then, or possibly my isc because it was reading 3 ohms on all of the pins...... I have attempted to find a new isc and was unsuccessful, dodge dealer says they are discontinued ...

 

[doggo]

He doesn't have the pins because he doesn't have a 2 bolt ISC.

Is the resistance test still the same for a 90?

I tried searching for a 90 ISC test but couldn't find anything that specifically stated the 91-94 test were the same, and my 90 manual is at the shop.

The 90 ISC is the same as the standard 91-96 1G 2G one. Tests the same, everything. It just has an 7" extension harness on it so it will connect to the '90 motor wire harness. A typical dodge dealer wouldn't know diddly about this '90 only ISC. They can be got, but they aren't cheap. Around $230 last time I looked. Numerous people with 90's simply buy the standard DSM ISC for 91-96, and crimp wire 8" extensions to the 6 pins. Works good.


Here is a pic of the 90 ISC if anyone is interested: http://info.rockauto.com/Airtex/Detail.html?2H1199.jpg


Regards
Doggo

 

[Auto RS T]

Thanks Doggo. I went to the garage today and checked out my 90 TB up close. I will edit my post to say "2 bolt ISC with pins", since obviously it is still held in with two bolts. I thought I had this 90-91 stuff figured out. Just another step closer.


Thanks for the knowledge.

 

[WeaselHack]

my multimeter must be screwed then, or possibly my isc because it was reading 3 ohms on all of the pins......

You are probably using the wrong setting on your ohm meter If your meter is set to 20K the reading would look like only 3ohms - well 0.03 ohms to be exact. Try a setting of 200 or 2K ohms instead (see pictures)

If your ISC is found to be hosed...check out this link: http://www.throttlebodys.com/DSMTBs.htm
The guy is selling them for $25 shipped with a guarentee! This is the same guy who sells the 63mm tbs - very reputable!

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[90_LASER_RS_420]

Ok, so i know i'm a noob at everything. But i do know that the isc you guys are showing me is completely different from mine, my throttle body looks like this:


http://www.throttlebodys.com/DSMTBs.htm

-the one directly under the "1990 Eclipse/Talon Turbo" text

So where the ^%$# is my isc?

 

[WeaselHack]

Correct! Your ISC IS different but the testing procedure is exactly the same. Just test the pins on the end of your 'pigtale' connector just like you would for a 1991+.

 

[90_LASER_RS_420]

May i ask a different question now then???
How do i remove my type of ISC???

 

[Auto RS T]

(Doggo) posted a link to what your ISC looks like, here it is.

http://info.rockauto.com/Airtex/Detail.html?2H1199.jpg

Your ISC is also held in by two bolts. Unplug the pigtail harness and follow it to your Throttle Body, that is your ISC. You can use a socket or a screwdriver on the two bolts that hold it in.

Circled in red is your ISC, Circled in yellow is one of the two bolts.

 

[90_LASER_RS_420]

All i have to say is thanks guys, i live in a small town and the one mechanic that we have sucks, well you know. I would way rather have any of you work on my car then any mechanic around here.

Thanks guys

 

[GSX_Dan]

Can anyone tell me how to test the harness side connector to the IAC on a 2G?

How does the ECU actually control the stepper motor coils? Pulsewidth? What should I be seeing on the 4 wires going from the ECU to the IAC?

I know the IAC is good and the ECU is good as I've tested them in a different car...so I need to test/repair the harness now...any help would be appreciated.

Thanks!

 

[luv2rallye]

It uses pulse width but if all you need is to check the harness, just check continuity from:
gray wire ECU pin 4 to IAC pin 1.
green/black wire ECU pin 17 to IAC pin 3.
gray/blue wire ECU pin 5 to IAC pin 4.
green/yellow wire ECU pin 18 to IAC pin 6.

ECU pinout: http://www.vfaq.com/mods/ecu-harness-2G.html

 

[GSX_Dan]

and that's exactly what I ended up doing, turns out one wire on the ISC connector was brittle and broke as soon as I went to test it! Problem solved!

 

[juntjoo]

hey I got the same exact issue. I'm still waiting for a reply from the vendor. 4&5 yield no resistance for me, and neither ISC, mine or this used one I just bought react at all when I apply 6v to it.

but check this out; I tested the voltage on the harness and according to Haynes manual you should get 12v from just one terminal. I got 12v from both 2&5. is that okay? anybody know what that indicates? Haynes has no plan B if this test comes out bad

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[RocCitySlayer]

I have tried 2 different ISC's and the resistense checks out fine but the plungers dont work. Im trying to check the connector that connects to the ISC to see if thats where my problem is coming from. I have looked at the FSM to find where the wires run to but had no luck. If anybody has any direct links or pictures that would help me out it would be much appriciated. Thanks,

 

[RocCitySlayer]

Is there not a way?

 

[RocCitySlayer]

Sorry to bring up an old thread but I figured it was already here so why make a new one.

My problem is I'm on ISC #4 now that I've tested. The voltage reader reads the coils fine but for some reason the plungers wont move. Any ideas of what the problem could be