Hey - my 1st post - found a lot of valuable info digging through the past posts on hear and using the search feature.

Thought I'd share my first experience trying an ECM repair this weekend - I just bought a used sidekick that wouldn't crank (so I got it cheap).  From searches here it sounded like it might be the computer... and it was...

I pulled out my ECM - the computer - its located on a small shelf above the brake peddle (more over the fuse box on the left hand driver side)- you can take off the speaker panel to get to the front bolt and the back bolt you can loosen from underneath it.  Its not the black box on the back - don't know what that is - its the metalic box you can see from behind the speaker panel.
 
Unplug the wire harness from the back and remove it - open the case up.
 
What makes the computer fail is a capacitor that will leak.  On mine, I was able to see the fluid coming out of it.

I saw two different capacitors - a 100 micro farad and a 50 micro farad.  I cleaned up the leaky fluid and noticed that it had burnt through a "trace" - the copper outline wiring thats on the circuit board.  I took the computer - still open - into Radio Shack and litteraly said "hey dude, you got any of these things?" and the guy looked it up (the one leaking on mine was the 100 micro farad capacitor) - and the Radio Shack guy said yep - they had a filing cabinet thing towards the back with capacitors in it.  I found the 100 mic capacitor (cost a $1.50) and bought a 5 dollar soldering iron kit.  Went home, and tried my hand at soldering...  which I didn't think I could do - but it wasn't really that hard when I started playing with it... just took about 20 minutes of fooling with it.
 
Heated up the soldering iron, put it on one end of the leaky capacitor - heated up the solder - worked it out of the board - did the same for the other leg of the leaky capacitor - pulling it all the way off.   Then I used a pocket knife to scratch the "trace" that had burnt through by the leak - exposing a little copper on each side - and melted a ball of solder on the exposed copper on each side - then bent a little piece of solder over - and fused it so that it made a little bridge repairing the burnt trace.   Then I cut the legs on the new 100 mic capacitor from Radio Shack to shorten it up some, and soldered it back in the holes from the old one. 
 
Then I just put the case back on the computer box, went out, plugged in the harness - cranked her up - and it actually worked!!  Cost me all of a $1.50 for the capacitor - and if it happens again I can fix it myself with a quick trip to Radio Shack.  My guess is it will last a few more years until it starts to leak again and burns through a trace again...  in the mean time I'm back on the road. 

The one thing I'm not so sure about (so I'm going to get a bad ecm from somewhere cheap and fix it and carry it as a backup) - is the tempature rating on the Radio Shack capacitor.  The one on the board was rated for a higher temp 105c  and the Radio Shack one was rated for 85c - but they looked exactly alike.  And since the higher temp rated one had failed - I thought maybe they just quit rating them that high and relabled them for lower temps or something.  Anyway - it'll be interesting to see how long and in what kind of weather it lasts.  I drove it all day Sunday and it was almost a 100 outside - no problems - of course it would take a while for it the fluid to eat through a trace again if it did start leaking... but what do I care it costs a $1.50 and only took 20 mins to fix - and if I start carrying a spare just in case

Now

If I could just figure out why I have to drive the transmission in first gear for about a mile in the mornings before it will start shifting (and then it works fine the rest of the day).

Welcome to Zukiworld!

Good job on the ECM.  I had a Ford Crown Vic that would not shift into overdrive until I drove about 1.5 miles most mornings.  I never could figure it out.  Now I shift the Zuk myself. .  Somtimes I miss the auto trans.
Jeff

From what I understand, the reason the capacitors leak is from inferior quality capacitors used in the construction of the ecm. Are the radio shack ones any better quality? I have no idea, but I would say they probably are. Did you clean the circut board really well so no more traces will get eaten unless you get a fresh leak? Great job!

Welcome to Zukiworld! Sorry I can't help you on the tranny. If it's an auto, maybe a bad torque converter or something? I really don't know...

I cleaned the board with a q-tip dipped in rubbing alcohol - it looked clean anyway.

I was thinking maybe it was heat that made the capacitors fail to begin with - so I think my next project is going to be cooling the computer box.  If I take a voltmeter to the pins coming in the back of the board, I bet I could find 12v to run a fan.  Then cut a hole in the top or back of the metal computer case and fit a computer CPU fan to it - blowing on the board -  and solder the fan power wires to the 12v coming in from the wiring harness.  I think that would work great - get some air flowing over those electronics instead of leaving them to generate heat in a closed metal box...  might need a small filter or something over the fan area to keep it from filling it full of dust though. 

The capacitors fail because of age, they are a lifed component and will usually last up to 10 yrs or so depending on usage. There are a number of parameters that affect their life, primarily ripple current and temperature. The temperature rating is very important, higher temperature devices are rated for a higher ripple current also and have much longer life so the Radio Shack capacitors are inferior to the standard items. There is a 12V switched supply from the battery that could be used to run a fan but I doubt if you would get any noticable improvement in life.
If you don't know about ESD then you should start reading up now because you should never even open up a modern electronic device without taking anti static precautions. I would always recommend taking the ECU to a local radio repair shop where they have the facilities, they don't usually charge much and it will be more reliable.

I'm familiar with ESD (unix sys admin for 10 yrs..) - took the same precautions I use while upgrading my pc components:

work in the kitchen on a tile floor, barefoot, using a wooden table

I would always recommend taking the ECU to a local radio repair shop where they have the facilities, they don't usually charge much and it will be more reliable.

I agree with you up to this point.  Why pay somebody $250 to fix a bad $1.50 cap?  That's just bad logic.

And - once all thoise IC's are soldered into the circuit board, they are actually MUCH less susceptible to ESD.

One question:

Did you really fix your broken trace with a solder bridge???

You would have been far better off using a short piece of the lead you cut off the new cap when you installed it.  That solder bridge will probably fail (of course they never fail, when you don't want them).

This whole thing, is the reason I'm building my next ECM (a MegaSquirt) from a kit - I will have all the schematics, and will be able to reprogram it, as needed, and add on whatever custom circuitry I want.  Yeah, it helps to be a former Electronics Engineer, and a current Computer Programmer, but it's not necessary, because the MegaSquirt documentation is so well written, and there's a complete forum like this one, for support.

MegaSquirt:  http://www.bgsoflex.com/megasquirt.html

One question:

Did you really fix your broken trace with a solder bridge???

Yeah - it was such a small break a little bigger solder ball would have bridged the whole thing - making the little bridge was more just playing with the solder to see I could control it enough to make the bridge.

Thanks for the megasquirt info - I'd rather get completely away from these ECMs too.

Welcome to the board

     Glad to see you got lucky on the ECU. I'll pass on a little info from being in the autorecycling/repair industry for 20 plus years.

FWIW
     Rhinoman is right that capacitors are a life component, but I've found that in most cases the failure is brought on by a problem downstream (bad ground, fuel pump dying, a superior stereo installation, etc) and usually knocks out not only the capacitors but especially in automatics, the fuel chip. Track/Kicks have been on a real run with ECUs for about 2 years now and I expect it will continue. Old age and dubious maint are terrible things.
     I've repaired 4-5 of theses things now for my own use as experiments and have found out of the 5, 2 were successful. The others failed again not long after.

     Finally have found a supplier that overhauls the little monsters, but that ain't cheap etheir, they replace the capacitors and have found a supplier for the fuel chips. They redo the complete board with new bits, re use the case and multiplugs.

FWIW

Zag

I'm familiar with ESD (unix sys admin for 10 yrs..) - took the same precautions I use while upgrading my pc components:
work in the kitchen on a tile floor, barefoot, using a wooden table

So...working on your computer in your carpeted living room with socks on while rubbing balloons on your head is bad ? 

Not for Bobzuki, he needs a dead ECU 

Not for Bobzuki, he needs a dead ECU 

Thanks Darrin!  I have my MegaSquirt Version 3 PCB ready to start building.  I realized that I dodn't need the MS-II at all, and that the V3 PCB will make doing MS-n-S easy!

As an Electronics Technician I know or we all know that engineers can't actually fix what they make. 

As an Electronics Technician I know or we all know that engineers can't actually fix what they make. 

I became an EE after several years as first an Avionics Tech, then an Electronics Tech, in an R&D environment.  Even built part of the original Hubble Space Telescope!  And I know EXACTLY what you're talking about.

As an Electronics Technician I know or we all know that engineers can't actually fix what they make. 

Ah but I was apprenticed as an Electronics Technician, I did my one year full time at college to get my first year EITB training and then day release to get my HND. I worked on the development of the Ring Laser Gyro building prototypes. Only later did i go to university and take my degree.