ISC fry and ECM??

[jswart26]

Is it really possible for the ISC to burn out an ECM? I took my car to the dealer and they informed my computer was burned out and I should replace the ISC cuz it probably caused it.

I tried to do the check w the 6v battery....but I'm not sure I did it right. I started the car and drove it around the block and no problems....but I don't want to burn out this ECM too.

Any advice? Should I replace it? Any help I'd appreciate.


-JS26

Also just so you know they wanted $900 for a new ECM, but its possible to purchase a rebuilt one at Autozone for $225.

 

[jmc94gsx]

From what I know there is a TSB regarding this problem, my buddy who worked at a Mitsubishi dealership told me about this. From what this has stated the ISC and the accompanying "idle surge" is the major cause of the capacitors leaking in the ECU's and their subsequent demise. I don't know the exact technical reasoning for this, perhaps too much resistance leading to an increase in heat and then the leaking cap destroying the ECU.

But this does hold a lot of truth upon my own observations, I have been around these cars since 1998. I had a bad ISC in one car, the ECU caps went. Upon conversations with other friends, cars with bad caps also had bad ISC's so there seems to be a strong correlation. And the cars I have owned or friend's cars that have not had a bad ISC's the caps were not bad upon replacement. I would like to know if people have noticed the same correlation and have experiences similar to what I stated.

So I will conclude that if your car has a bad ISC currently don't ignore the problem, fix both the caps and the ISC ASAP.
And lastly is the ISC was replaced in the past, get the caps replaced as soon as you possibly can if not done already

ALso you can get used ECU's from places like M&S recycling or look for people parting out cars.

 

[laserturbo91]

so where is a decent place to get a new/used isc?

 

[Thunderskull]

I've had the same thing. I had a bad ISC take out 2 different ECU's. The second time, the ISC had a catastrophic failure and my ECU actually caught fire. That was a feeling I'd rather not repeat.

Originally posted by jmc94gsx
From what I know there is a TSB regarding this problem, my buddy who worked at a Mitsubishi dealership told me about this. From what this has stated the ISC and the accompanying "idle surge" is the major cause of the capacitors leaking in the ECU's and their subsequent demise. I don't know the exact technical reasoning for this, perhaps too much resistance leading to an increase in heat and then the leaking cap destroying the ECU.

But this does hold a lot of truth upon my own observations, I have been around these cars since 1998. I had a bad ISC in one car, the ECU caps went. Upon conversations with other friends, cars with bad caps also had bad ISC's so there seems to be a strong correlation. And the cars I have owned or friend's cars that have not had a bad ISC's the caps were not bad upon replacement. I would like to know if people have noticed the same correlation and have experiences similar to what I stated.

So I will conclude that if your car has a bad ISC currently don't ignore the problem, fix both the caps and the ISC ASAP.
And lastly is the ISC was replaced in the past, get the caps replaced as soon as you possibly can if not done already

ALso you can get used ECU's from places like M&S recycling or look for people parting out cars.

 

[Moosh]

Hello. The search tool is awesome! The same exact thing happened to my car two weeks ago. I was driving and suddenly smoke started coming out of my ECU. I opened it up and saw damaged resistor packs. The resistor packs go straight to the ISC motor coil pins I believe 4,5, 17, 18 on the 2G turbo ECU. If I unplug the ISC the car drives with the burned ECU and the resistor packs do not heat up. If I hook up the ISC the resistor packs heat up. The damage and overheating seems to be directly caused when the messedup ISC is hooked up.

I just got a new ISC and the old ECU still gets hot like a mofo, so I put a new ECU in and the resistor packs are not getting hot at all. I am still worried though that suddenly my new ECU might smoke randomly as I am driving. Do you guys think I will be okay with the new ECU and ISC? The new ISC still causes the OLD ecu to get hot, but it does not cause my NEW ecu to get hot. I am trying to figure out if there is a possibility that my ECU will smoke just like the last one did. Please let me know what you guys think.

 

[stockmkt8r]

Did any of you hear 'ticking' noises coming from the dash when you had this problem? I have a bad ISC motor and will replace it ASAP. No smoke yet, thank goodness, but I'm starting to hear 'clicking' noises.

Thanks!

Best,

Dan

 

[Thunderskull]

Yes, that's your ECU. I'd pull it out, open it up, and check the capacitors for any leaks. If you still have that clicking when you replace the ISC, then you will also need to get yourself another ECU.

 

[stockmkt8r]

Originally posted by Thunderskull
Yes, that's your ECU. I'd pull it out, open it up, and check the capacitors for any leaks. If you still have that clicking when you replace the ISC, then you will also need to get yourself another ECU.

How do I check the capacitors for 'leaks?'

Thanks so much for helping me out man.

 

[Thunderskull]

I just noticed that this problem is on your 2g. The capacitor problem is nearly always a 1G issue. It could be your ISC clicking. I also read your other post and saw that the problem goes away when you're over 1000 rpms. I doubt this is a problem with your ECU. I think there's a solenoid that could cause clicking like what you're describing. I think it's the fuel pressure solenoid, but I'm not 100% sure. I'm on vacation right now and don't have the service manual handy. When I get back on Monday I'll post again when I'm sure. Make sure it's not coming from your engine compartment. It might be your ISC clicking also. BTW, did you pull and test the ISC to make sure that it's going bad? If you need the procedure, go to www.vfaq.com. There's a vfaq there that tells you the procedure. I think it's under intake or electrical.

 

[stockmkt8r]

Thunderskull, thanks so much for taking the time to help diagnose my car! I actually figured it out, it was my UICP knocking really hard on a peice of metal. WHen I held the UICP still, it stopped knocking. It was really strange though because it definitely appeared to be coming in from the cabin. Oh well, I got taht figured out.

Thanks for the link to the ISC testing procedure, I'll most definitely have to do that.

Best,

Dan

 

[OhmegaMike97awd]

Since electronics is my area of experise, I'll share my opinion. The chicken or the egg relationship between ISCM and caps? Who knows? The reality is, if the caps are bad, the ISCM will try to move out of it's range, and fry itself. I don't really believe the ISCM takes out the caps.

The capacitors in the ECUs fail primarily due to their age, and the wide temperature ranges that occur inside the car. From winter weather, then the heater running, and summer's heat, and A/C running. These huge temperature changes, (and the fact that the caps voltage specs were a bit under-rated for the circuit) all cause them to fail.

I have repaired probably 100 mitsu ECUs with bad caps, in DSMs in Geo's, Nissans, etc. When a ECU burns up/smokes, it's burning up because the circuit board has been so badly damaged from the corrosive liquid oozing from the capacitors, that it can no longer carry the current needed thru it's traces (circuit paths etched on the circuit board).

I wouldn't say it's ONLY a 1G problem either. The caps in a 2G will find the same demise in time. I have a 97' 2G TSi, and I've replaced the caps in mine just to be safe. When you see/hear/smell a symptom, it might be too late!

Just my 2cents...

Now, will somebody help me diagnose my idle problem! Please!

 

[Thunderskull]

Originally posted by stockmkt8r
Thunderskull, thanks so much for taking the time to help diagnose my car! I actually figured it out, it was my UICP knocking really hard on a peice of metal.

I'm glad it was something simple. I wish my DSM problem was so easy. I cracked my subframe. I'm back home in the midwest and just happened to run across a guy parting out his Talon. We just pulled out the one from his and I'm bringing it back with me on the plane to California. This thing is going to be such a PITA to get in. The engine was out in the parts car and it took us 2 hours with air tools. It's going to take me at least 6 hours to get mine out and the new one in. I just hope I don't break any bolts.