The Authoritative Galant VR-4 Resource

Join the best E39A 1991-1992 Mitsubishi Galant VR-4 community and document your GVR4 journey.

  • Software Upgraded - Reset Your Password to Login
    In order to log in after the forum software change, you need to reset your password. If you don't have access to the email address you used to register your GVR4.org account, you won't be able to reset your password. In that case, follow the instructions here to regain access to the forum.

Cooked ECU - deep fried - with pics.

Turbo4door1

Well-known member
Joined
Feb 20, 2003
Messages
1,523
Location
Kearneysville, WV
Well, I was going to take my Galant to get inspected tomorrow. I uncovered it, cleaned it up a bit, and decided to take it around the block - considering it is the first time I have been in it in about six months. Well, about half way around the block, I heard the ECU "click", the check engine light came on, and I lost power. I pulled over, shut the car off, and checked all the fuses and fuseable links. Everything appeared okay. I started it back up and drove home. It wouldn't idle when coming off throttle and I could smell the electrical burning smell. When I pulled in my driveway, I shut it off, and could visibly see the smoke coming from the passenger side of the dash. I jumped out and pulled the battery cable off. I pulled the ECU out, and below is the resulting carnage:









So, it appears whatever that row of black things is are toast. The caps look good, have been previously replaced, and don't appear to have leaked. The soot/smoke appears to have just drifted on to my DSMLink chip - and I am HOPING it isn't damaged.

Does anyone have ANY idea what would have caused this?

Who is currently the "go-to" guy for ECU repair? From what little can be seen in the pictures, does this even look repairable. And lastly, if someone reads this, and has a good socketed ECU they would like to unload, please shoot me a PM.

Thanks. /ubbthreads/images/graemlins/banghead.gif
 

ktmrider

Well-known member
Joined
Sep 10, 2007
Messages
3,124
Location
Portland, OR
Ouch.
SteveP or Terry Posten are the folks to talk to.
 

mistaVR4

Well-known member
Joined
Dec 16, 2003
Messages
4,768
Location
Boulder, CO
That sucks man! I would say you should most definitely remove and test (per the FSM) your ISC motor before you even plug in another ECU or it will instantly ruin the new one you put in, the black driver(s) are associated with the ISC motor and when it fails that is the result you get with any ECU. It sucks, I've had it happen to me and lots of people here have too. Depending on how bad it burned the board, it can most likely be repaired by the folks mentioned above.
 

stevep

Well-known member
Joined
Oct 23, 2004
Messages
415
Location
St. Charles, IL USA
Quoting Turbo4door1:

So, it appears whatever that row of black things is are toast. The caps look good, have been previously replaced, and don't appear to have leaked. The soot/smoke appears to have just drifted on to my DSMLink chip - and I am HOPING it isn't damaged.

Does anyone have ANY idea what would have caused this?



Your ISC or the cable is shorted. Those black things are the drivers for the ISC and the ones not burned up are for the various solenoids.

It's made a big mess but this damage is usually repairable. It's smells worse than it is. /ubbthreads/images/graemlins/smile.gif

You need to measure the coil resistance in the ISC and order a new one if they are less than 20 ohms or more than 40 ohms. If the ISC isn't shorted or open now you need to check the wiring harness to the ISC for shorts to the 12v wires running to the center upper and lower pins of the ISC.
 

89coltgt

Well-known member
Joined
Mar 14, 2006
Messages
1,027
Location
Ste Genevieve, MO
^^ Steve is the man when it comes to repairing damaged ecus, he has done all of mine and they are all going strong /ubbthreads/images/graemlins/worthy.gif
 

Terry Posten

Well-known member
Joined
Dec 16, 2003
Messages
9,009
Location
Davenport, Iowa USA
Yep, Steve is right. The black stuff is conductive and must be cleaned off prior to replacement and repair of the traces.

I would not want to attempt that repair job because I can't test it properly to the level it will need to make sure everything is back to normal.

Steve would be my recommendation.
 

Turbo4door1

Well-known member
Joined
Feb 20, 2003
Messages
1,523
Location
Kearneysville, WV
Thanks guys.

A few more questions. I still have coolant going through my throttle body. Is it possible I finally got a leak that shorted the ISC and took the board out in this manner?

Also, would a short at the battery cause this? I have a battery tender I keep on the car. There is about a 15" pigtail that stays connected to the battery when I unplug the tender. When I went back out to look under the hood last night, I noticed the "cap" for the plug end of this wire had come off which left one of the two pins for the plug exposed. I didn't trace it back to the battery yet, but I am HOPING the exposed pin was the negative side and not the positive. Assuming it was the positive, and it was shorting the positive side of the battery to the chassis of the car, could it have caused this damage? The pigtail would have been flopping around in the area where the battery used to be. That's where I tuck it when I unplug it.

Thanks for the tips on the ISC. I will definitely throw a meter on it and test it out. I will be checking everything I can prior to plugging another ECU in. I live pretty close to the ECM Tuning guys (about 25 miles), so I think I might just take it to Dave Mertz to get checked out repaired. They can check out/clean my DSMLink chip while they are at it - to make sure it isn't damaged too.
 
Last edited:

Quote:
I still have coolant going through my throttle body. Is it possible I finally got a leak that shorted the ISC and took the board out in this manner?


Yes, that is exactly what often causes this. The big O-ring for the FAIV leaks, and coolant gets into the ISC and shorts it out. When you pull the ISC out, look for discoloration from coolant on it.
 

Turbo4door1

Well-known member
Joined
Feb 20, 2003
Messages
1,523
Location
Kearneysville, WV
Okay, I went out and pulled the ISC - and as suspected, it is bad. Here are the readings between the pins:

1 - 2: 34.8 ohms
2 - 3: 9.6 ohms
4 - 5: .5 ohms
5 - 6: 36.9 ohms

I want to keep my ISC (due to the A/C and power steering). Aside form getting a new ISC, is there anything I need to do with the FIAV to make sure this doesn't happen again right away. I don't notice any clear signs that the FIAV leaked and caused the ISC to short, but assuming that is what happened, what else do I need to replace to be sure this doesn't happen again anytime soon?

Is it typical for the ISC to short without the FIAV leaking coolant on it?

Lastly, is JNZ about the best place to order the new ISC?

Thanks.
 
Last edited:

Terry Posten

Well-known member
Joined
Dec 16, 2003
Messages
9,009
Location
Davenport, Iowa USA

GVR4_1057

Well-known member
Joined
Sep 3, 2008
Messages
676
Location
Brucetown VA
I have had great luck with the 2G black ISCs. Sometimes the 1G ones will test good but still idle bad due to wear. Now that I have gone black I have no intention of going back.
 

Ian M

Well-known member
Joined
Jan 11, 2002
Messages
2,348
Location
Martinsburg,WV
Quote:
Is it typical for the ISC to short without the FIAV leaking coolant on it?




Yeah,in fact most companys will not warranty reman ECUs unless the ISC is also replaced.

I just made a blockoff plate and deleted the ISC and FIAV. No complaint with idle,even using the AC. I've already had one FIAV leak and short out the ISC,not taking the chance again.
 

Turbo4door1

Well-known member
Joined
Feb 20, 2003
Messages
1,523
Location
Kearneysville, WV
Quoting Terry Posten:
www.throttlebodys.com sell them. I think I saw $50 for a 1G style. They are rebiult (I think).



Thanks Terry. I contacted Steve and have one of his rebuilt ones on the way. He seems like a great guy.

Billy - the one that was in my car, that shorted out, is one of the 2G Black ISCs. Go figure. /ubbthreads/images/graemlins/dunno.gif

Ian - thanks. I ordered an FIAV o-ring gasket too, so I guess I will pull the throttle body off and at least replace it too - just in case.
 

thats some crazzzy ish!!! I hope your dsmlink is ok! I have never seen isc drivers go up in smoke like that! The car didnt fill up with a big cloud of smoke like when a cap goes? I guess ya gotta start hunting for a ecu now eh? Best of luck, i had my TB rebuilt by steve @ throttlebodies.com so i hope this doesnt happen to me.
 

Terry Posten

Well-known member
Joined
Dec 16, 2003
Messages
9,009
Location
Davenport, Iowa USA
I JBwelded the FIAV section completely closed. I kept the ISC paths and now just run it that way.

Runs perfect, but my car never sees cold weather.
 

deez

Well-known member
Joined
May 29, 2004
Messages
1,150
Location
Chico, CA
So the 2G ISC and 1G are compatible? No problems switching the two out?
 

GVR4_1057

Well-known member
Joined
Sep 3, 2008
Messages
676
Location
Brucetown VA
No problem at all. It is a plug and play situation.
 

Launch

Well-known member
Joined
Aug 17, 2006
Messages
350
Location
Texas
Ive taken the ground wire from the harness-ISC and made a ground strap to firewall. Why such a strong stepper motor has no ground other than to board i have no clue.
 

deez

Well-known member
Joined
May 29, 2004
Messages
1,150
Location
Chico, CA
So then why use a 2G vs. a 1G??
 

Quoting Launch:
Ive taken the ground wire from the harness-ISC and made a ground strap to firewall. Why such a strong stepper motor has no ground other than to board i have no clue.



I don't see how grounding the ISC will do any good. The coils get pulsed to ground through the ECU, but nothing inside the ISC is grounded at all. /ubbthreads/images/graemlins/dunno.gif
 
Support Vendors who Support the GVR-4 Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications RixRacing RockAuto RTM Racing STM Tuned

Recent Forum Posts

Top