Burnt ECU, not capacitors

Well... after swapping throttle bodies I turned the key on, opened up my gameboy (interface for DTEC tuner) and left the key on for about 3 or 4 minutes at which point I started to smell burnt electronics. Never started the vehicle. Turned the key off, disconnected the battery and found some smoke under the dash by the PCM. Pulled the PCM and took off the cover to find this...

I'm hoping at least one of you (Terry/KeyDiver) can help me out here and possibly know what it is that this particular part of the ECU controls so I can figure out what may have shorted out. Or... if this is just a freak occurrence and the car decided it doesn't want me driving it anymore. To the best that I can tell, it looks like that chip, or whatever it is, has the circuit label "R33" next to it, if that helps.

Secondly, and I'll add a post in the Wanted section, it looks like I'll be needing to purchase a new ECU. If anyone can help me out in the least bit I would be greatly appreciative.

-Chris

 

[Terry Posten]

ISC drivers.

Fixing it is about a 15% chance. Most of the time, the board is cooked so bad that it falls apart when you remove the parts.

I can try to fix but if the board is cooked (most likely is), its done for.

I only charge $5 for each driver plus $20 for labor. But like I said, it does not look good.

 

ISC as in Idle Speed Control, right? Just off the top of your head what all do you know that could have caused that? I don't have a wiring diagram in front of me to show what's on that circuit. I'd hate to go through the hassle to have you repair it, or purchase another ECU just to plug it all back in and have a bad sensor fry it again.

Thank you very much, Terry!

 

[Terry Posten]

Meter your ISC to make sure you have 30ohms at each of the 4 coils. www.vfaq.com for directions.

You can also meter the wiring to make sure you don't have a short or a grounded issue.

The black spray the spewwed all over the processor is conductive and is almost impossible to get off as well.

Good luck.

 

Here are a couple close up pictures of the damage in case you can make a better assessment on repair possibilities.

 

Quoting Terry Posten:
Meter your ISC to make sure you have 30ohms at each of the 4 coils. www.vfaq.com for directions.

You can also meter the wiring to make sure you don't have a short or a grounded issue.

The black spray the spewwed all over the processor is conductive and is almost impossible to get off as well.

Good luck.




Have a spare ECU for sale?

 

Well that did it, ISC pins 5-6 had only 3.8 ohms. Wonderful. Try to fix one small problem (vac/boost leak at the throttle shaft) by rebuilding an extra TB that I had which already had the electronics on it and now I've got 200 dollar piece of plastic scrap. Wonderful.

Thanks for your help Terry, and again anyone that has a spare EPROM ECU I'd GREATLY appreciate the heads up. I was supposed to enter into a tournament this friday =(

 

[Terry Posten]

No, but Keydiver does and they have never and will never have acid issues.

That looks bad. I'll look at it but can't promise anything.

 

Thanks for helping Terry but if the odds are that slim of being able to repair it then I'll just put the shipping charges into purchasing a new ECU.

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

 

[Terry Posten]

Keydiver may give you a small credit towards a new one from him for your old unit.

 

Has anyone ever tried wiring a couple 7.5 amp fuses between the ISC and the ECU as a safeguard? This seems like an awfully costly problem to have that is fairly unavoidable in the event of a failure of the ISC.

*edit*

Spoke with one member and he brought up the point that it takes VERY little current to damage ECU components so even a 7.5 amp fuse might not work. Hmph, it's a shame that this is such a delicate part of the car. Even though Mitsu recommends replacing your ISC with a new one any time you replace the ECU to prevent damage, there's still no safeguard against an ISC in the event that it goes bad over time.

 

[stevep]

The drivers blow way to quickly for a typical fuse to protect.
It's max rating is something like 2A for 20 ms.

I don't think that ECU is that bad off. I get worse ones here all the time and they leave working.

 

[Jostar]

Steve FTW!!!!