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Is my ECU dead?

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GooeyGus

10+ Year Contributor
459
1
Sep 23, 2009
Marysville, Washington
I dedicated my entire Sunday to talon maintenance today. I started off by pulling the ECU to check for cap leakage. Everything looked perfect inside, not even a hint of anything wrong. I popped the ECU back in and went for a quick drive; everything was great as usual.

I got home and decided to change my oil. I had to borrow a wrench from the neighbor to get my oil filter off, but other than that everything went smoothly. After I finished I started the car to make sure there were no leaks, everything looked great.

After I got cleaned up, my girlfriend and I were going to grab some food. We hopped in the talon and drove down the street. I made a quick stop at my neighbors house to return the wrench and left the car running in the road. As I walked away the car shut off. I asked my girlfriend "why did you shut the car off?" she replied that she didn't touch anything. I had been having a few idle issues lately so I didn't worry about it, but thought it was very strange how it literally sounded like someone turned the key off.

Sure enough, I got back in the car and it wouldn't start. Not even a little sputter, we're talking totally dead.

Crap.

So I began to diagnose. The check engine light wAs on. "great!" I thought. The codes should tell me what is wrong and I'll have this thing back on the road in a couple hours.

I proceeded to check the codes, but got absolutely nothing. Again, the CEL is on, but no codes. I didn't even get the 'heartbeat' of a healthy ecu.

I proceeded to check every fuse and relay that I could think of, but found nothing wrong.

One weirs thing I found... The MPI relay clicks like it should, but usually it stays on for like 10 seconds after the key is out, then I hear a "click" signifying that the ECU has shut down. Well, now the MPI clicks off the second the key is turned off.

So what do you guys think? Is the ECU toast? Is it possible that a capacitor has died without leaking? I will try replacing them tomorrow.

Here is another tidbit that I think might be relevent:
about a year ago, while I was driving home, I heard a click and the CEL came on and shut off a few seconds later, like the ECU just reset itself. This happened a total of maybe 3 times in a year-long period, but hasn't done it for around 6 months.

I'm sorry for the long post, but I wanted to be thorough.

What do you guys think?
 
i dont think its the ecu.i had about the same proble afew months ago and this fix mine. there is a little gold box next to the ecu it would click on and off fast. befor i even shut the car down i replaced it and was fine after that.
 
I proceeded to check the codes, but got absolutely nothing. Again, the CEL is on, but no codes. I didn't even get the 'heartbeat' of a healthy ecu.

Sounds like you may need a new Ecu... .put you ecu in a another 1g and see what it does... I wouldn't put another in till you figured out what caused it take $hit though if it does end up being it...
 
Make sure all the plugs on the ecu are pushed in all the way!!
 
i dont think its the ecu.i had about the same proble afew months ago and this fix mine. there is a little gold box next to the ecu it would click on and off fast. befor i even shut the car down i replaced it and was fine after that.

That is the MPI relay. I've already checked mine and it's fine.

The plugs are all the way in, and I'm trying to find another 1g to swap it into.

I need to check my brothers garage after work... We may have a spare ECU laying around
 
its almost certain its your ECU, i have the same issue, if you smell ## ecu and it smells burnt/wrotten slightly u fried it. i finaly found another stock ecu but i might save up and get a EPROM instead since i plan on getting ECM Link. G/L with it all man
 
I ordered a new/rebuilt eeprom ECU (since I already had a freakin' eeprom ECU... I couldn't live with myself if I downgraded... haha) on ebay (from a seller that I've seen a few people recommend) for $250+$100 core. I'll plug it in when I get it and report back.

I found a leaky cap on my ECU (just BARELY leaked anything... the fluid didn't even make it out from under the cap). I replaced it but it didn't fix the problem.

The cap is supposed to be a 50V 47uF, I used a 50V 100uF. Does anyone know if it would matter in this application? I figured these were just power supply filter caps on the ECU so the capacitance wouldn't really matter as long as I didn't go below the original rating.

Either way it didn't fix the problem. The cap that was leaking was the one closest to the transistor heatsink, the one that is all by itself. Can a blown cap that didn't piss cap juice everywhere really blow the whole board?

another update, I am getting voltage at a couple sensors (ISC, MAS) so it seems like at least the voltage side of the ECU is working... it's like the brain just wont boot up. Even when I intentionally disconnected a few sensors I didn't get any codes :sosad::sosad::sosad:
 
That is odd


Thanks for the help.

UPDATE:

With they key on, I just noticed that the factory boost gauge does NOT move to zero like it should if the ECU were doing its job.

Hopefully my new ECU gets here soon.... :sosad:
 
I popped the new ECU into the car a few days ago and it started right up. Seems to be running good!

Thanks everyone for your input!
 
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