2G I believe I just fried the ECU

Ludachris · Nov 14, 2010

Yesterday I drove to the store and came out and tried starting the car (my recently purchased 97 Talon TSi)... sounded like it was running on two cylinders for a few seconds and it died, then kept dying when I tried starting it like 20 times, still same odd running sound. When the tow truck arrived a half hour later it started just fine but threw a CEL. I drove it home with no problems. I checked the code with a scanner and it read P0340, cam position sensor. The car was still starting just fine today and idling fine. I couldn't see any issues with wiring.

I took it for a test drive up the street, all the sudden it dies completely and a big puff of smoke comes from the dash, I'm thinking ECU. I turned the key an no power at all. I had to roll the car back to the house. I pulled the ECU expecting to see a black or brown fried board and didn't see that. The only thing I could see were 2 or 3 capacitors that looked like they were bulging slightly, though I have no idea what a bad ECU would look like. No liquid mess or anything like that. I tried taking a photo but couldn't get it to focus close enough to see the capacitors. Are the bulging capacitors a big enough sign that the ECU is fried?

My questions are - is there anything I should look for before I plug in my new ECMlink ECU? I noticed some bare wire on the ECU harness near the plug, where there was likely a S-AFC at one point. I plan on fixing that. But anything else I should look at that might have caused the old ECU to fail? Would a bad cam position sensor fry the ECU? I'm afraid to put in my new ECMlink ECU and fry it too.

XiKeiyaZI · Nov 14, 2010

If it were me, I'd pull the dash and start checking for wires that were rubbing the frame in any way, but that's just because I get overly cautious with wiring to avoid the event of a fire due to an unseen fire hazard. Definantly check for the source of the issue, besides the ECU, before you slap a new one in there. I can't really say that I see an ECU causing a huge plume of smoke to exhaust from your dash, especially if you said that the interior of the ECU didn't look too bad. If something fried bad enough to do that, you'd notice it when you opened the case. I bet there's something up with the harness, specifically related to the wiring for the sensor. It could be grounding out causing the symptoms you've noted.

As for ECU's, I have no experience besides pulling the board out, looking it over to bad traces, checking the caps (which you said looked as if they were bulging a bit), and seeing if there are noticeable burns. Could we bug you to post a few good pics of the accused 'culprit' ECU? I'm sure one of the ECU guru's would have a few things to say with that benefit.

ktgurl87 · Nov 14, 2010

this probably won't help you... BUT... when my cell phone battery was having a hard time charging, it got really hot, and very swollen. i'm thinking your capacitors got hot. which if you go by what kei's saying... if a wire is rubbing the frame, could be causing a ground issue i would think, which is turn could help the capacitors along in their farewell journey. but i would also pull the dash and look at all the wires as well. make sure nobody's naked in there... go ahead and take a day to make you feel better about your car's wiring safety

pazsion · Nov 14, 2010

bulgeing or crispy capacitors is a sure sign of an over voltage... the mfi was doing it's job by killing the car..i bet a relay got a bit of a spike and it got through one good time..and cooked those caps..
a pinout or board scematics could help pinpoint where it is.. take care of it be4 u buy a new ecu

i have 2 lose wires that run along the intake.. black/orange OR black/red will kill my car.. was told those were sopposed to go to a maf or map sensor

EagleTSIawd · Nov 14, 2010

You might have fried one of the ecu grounds if there was a short on one of the sensors.

heres a link from ECMLink on where to find the fried ground and repair it:

blownsensorground [ECMTuning - wiki]

and here is a link that compares a good ecu vs a bad ecu:

ecurepairhome [ECMTuning - wiki]

Hope its just the ecu you are dealing with or else it might be a pita trying to find out which sensor has a short

gofer · Nov 14, 2010

In my opinion it doesn't sound like the ECU is the culprit here, especially if your getting the CAS CEL. I hate to say it but its time to pull out a multimeter and check for voltage at the CAS with the key in the "ON" position.
CAS Testing:

Disconnect the sensor and measure on the engine harness side with the key in the "ON" position.
- BLK (Pin 1) - Ground (0 ohms to ground)
- BLU/RED (Pin 2) - 4.8v to 5.2v
- RED (Pin 3) - 12v
If everything checks good with a multimeter plug the CAS connector back in and check voltages with the engine cranking.
- BLU/RED (Pin 2) - 0.4v to 3.0v (If your reading 0v while cranking then the CAS is dead)

I've also had similar problems Chris and it wasn't the CAS itself but the connector on the CAS. It had a hairline crack that wasn't noticeable unless you took a close look, it was very intermittent and hard to chase down. The fix was just replacing the CAS but finding the crack took a few days...

The easiest way to verify the ECU's operating is by turning the key to the "ON" position and ensure that the CEL is coming on for 5 seconds. If something on the ECU, like a capacitor, has blown it will smell like rotten fish and you definitely can't miss the scent.

As far as the puff of smoke from the dash goes I'd check the fuses and hopefully something blew that way it gives you somewhere to begin chasing wires for a short.

numbertwelve · Nov 15, 2010

before buying a new ecu or doing some other off course action if you have ANY wires wrapped with electric tape / bare or anything like that make sure they arent touching each other or anything metal. if your ecu was out your CEL wouldn't be on and for the 2 cylinders part my recently purchased 97 gsx was running amazing until i put the front bumper cover back on. i got in started her up and i was running on 2 cylinders after about 30 minutes of head scratching it turned out to be my side marker wires were stripped a bit and touching one another.

Ludachris · Nov 15, 2010

Just to clarify here guys, the CEL came on before the car died and before the puff of smoke that led me to believe it was the ECU frying. I haven't tried turning the car on since that happened.

Looks like I'll be tracking down some wiring and checking voltage.... yay. I'll plug the old ECU back in to see if it still works.

Ludachris · Nov 15, 2010

Photos of the ECU... still couldn't get a good close-up of the capacitors. Need to figure out the right setting on my camera. I pointed to the ones that are bulging with green arrows.

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ramsack · Nov 15, 2010

Capacitors don't smoke when they blow. They explode with a loud pop. I think you may be lucky enough to just find a wire shorting out somewhere. From the photos the ECU looks pristine, no hotness to the black drivers, and the caps look good. What did the burning smell like? Anything burning in the ECU would be instantly visible, and be visible on the cover.

gofer · Nov 15, 2010

Chris you need to get a camera that can focus inside 12" LOL

Like someone mentioned above, its possible that you blew the ECU's sensor ground going to pin 92 on the wiring harness. 2g ECU Pinout Your ECU sensor ground looks funny in the pictures, it looks like a WHITE track mark there from what I can tell. Heres a picture of a repaired sensor ground...

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Just remember that if the sensor ground is blown you need to figure out whats causing it to blow or it will just do it again.

ramsack · Nov 15, 2010

To me it looks like the white silkscreening they use to mark components, possibly for the point of spotting a blown ground quicker when an ECU technician at Mitsu may be inspecting them.

AlaskanDsm · Nov 15, 2010

Checkyour camera for a Macro selection... I think that is what it is called for up close pictures of flowers and bugs and such... should work ok for this too!

XiKeiyaZI · Nov 15, 2010

I have to agree with the above stated - Even with an undetailed picture of everything up close that ECU looks fine. A Bulging cap usually looks like this.

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The top cover piece is what's usually going to expand and rupture, not the sides. It wouldn't hurt to look a little closer, especially in the area that was mentioned above.

This really sounds like a grounding issue, though. Good luck with tracking that down. I know me + wiring = headache.

Ludachris · Nov 15, 2010

So a quick update.... I think I found the issue. I opened up the dash, ripped out the stereo receiver, the turbo timer, the aftermarket gauges, and everything else I could find - what a mess someone made of the factory harness. I came across a bare wire connection for the stereo and a few questionable wires where things were spliced in. I removed several wire connectors and taped up everything as good as I could. I have a feeling this was all due to a bare wire touching metal. Turns out the Ignition fuse was blown. Popped in another one after I put everything back together and the car started right up - using the ECU I thought I fried. Finally, some good news.

Still not sure how this could have resulted in the car running on 2 cylinders when I went to start it yesterday, and it not wanting to run. But I'm hoping it's all part of the same problem.

I plan on driving the car to work tomorrow... keep your fingers crossed for me. Hope I don't get stranded.

steve · Nov 15, 2010

The ECU looks fine (for as much as I can see), hopefully you fixed up the wiring mess. One of the first things I do when I get a "new" car is rip out and fix all the aftermarket wiring since it's usually so poorly done. It saves so many headaches later.

ramsack · Nov 15, 2010

steve said:
The ECU looks fine (for as much as I can see), hopefully you fixed up the wiring mess. One of the first things I do when I get a "new" car is rip out and fix all the aftermarket wiring since it's usually so poorly done. It saves so many headaches later.

I do the same thing. Luckily only own personal car there's only been wiring under the hood that needed to be addressed, nothing on the interior. Which is nice. I would rather work on an engine harness than a chassis harness, as far as not needing to gut stuff to get to the wires or laying on the floor upside down under the steering column. I also find it nice to dress up the harness right away because all I ever need to buy is heat shrink tubing an electrical tape. Literally A few dollars to spend on less headaches in the future and possibly saving in the future from the work. The downside is time. I learned electronics from engineers and books since I was single digits in age so I am able to divide the workload up by knowing what systems I can work on and not need to do anything else so I can still drive the car.

mindset · Nov 15, 2010

Ludachris said:
Still not sure how this could have resulted in the car running on 2 cylinders when I went to start it yesterday, and it not wanting to run. But I'm hoping it's all part of the same problem.

I believe there is two ignition fuses. Correct me if I'm wrong. But when one of mine blew it acted the same exact way. It would turn over, ignite 2 cylinders, and never get rolling. And to be honest, I'm pretty sure I thought my ECU was blown too.

XiKeiyaZI · Nov 15, 2010

Ludachris said:
So a quick update.... I think I found the issue. I opened up the dash, ripped out the stereo receiver, the turbo timer, the aftermarket gauges, and everything else I could find - what a mess someone made of the factory harness. I came across a bare wire connection for the stereo and a few questionable wires where things were spliced in. I removed several wire connectors and taped up everything as good as I could. I have a feeling this was all due to a bare wire touching metal. Turns out the Ignition fuse was blown. Popped in another one after I put everything back together and the car started right up - using the ECU I thought I fried. Finally, some good news.

Still not sure how this could have resulted in the car running on 2 cylinders when I went to start it yesterday, and it not wanting to run. But I'm hoping it's all part of the same problem.

I plan on driving the car to work tomorrow... keep your fingers crossed for me. Hope I don't get stranded.

Glad to hear that it really wasn't anything major. It's sad that people get in such a rush and don't go about doing things correctly. There's no telling what loose/bare wires can lead to. Something as simple as the issue you were having all the way to a burning engine harness.

Not wanting to toot my own horn here... but who called it? -nudge-.

Ludachris · Nov 16, 2010

Thanks for all the suggestions guys. I probably should have ripped open the dash right when I bought the car, but oh well. I drove the car to work this morning and everything seems fine. I'm hoping it will stay that way.

snowborder714 · Nov 16, 2010

FYI, to take close up pictures, Matt had it right. Look for a little flower icon on your camera to activate macro mode.

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2G I believe I just fried the ECU

Ludachris

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gofer

numbertwelve

Ludachris

Ludachris

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gofer

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steve

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mindset

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