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Fried ECU?


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Hey everyone wish I could be making a post about something positive for once.  Went to start my 02 pathfinder earlier and it would crank constantly and not start.  Tried again and the engine turned over and started but immediately died.  This happened twice and since that last time it will not start anymore.  Initially my thoughts were ignition coils possibly or fuel pump but I believe I hear the fuel pump prime when I turn the keys to ignition.  I don't think it has to do with my throttle body (drive by cable).  I cleaned it around a year ago and its been function fine ever since.  Never had any codes or weird idling after cleaning the TB.  I have this sneaking suspicion that it might be the dreaded IACV failure.  Maybe this is unjustified but it seems that these symptoms do fall inline with this possibility as far as I can tell from forum posts.  Maybe this is relevant but I will say one weird thing that started maybe in the last 5 months is my yellow 4WD illumination light on the dash will randomly come on for maybe a minute or two and go away.  This happens while I'm in 2WD (Electric All-Mode System).  This is of course rare and has only happened I believe twice in those 5 months.  No idea if this is a warning sign for a failing ecu or not, just thought I might mention it.

 

One last thing to note, the truck drove fine earlier that day maybe 2 hours before this all happened.  What are the symptoms of a failed ecu due to the IACV seal failure?  I'm sure it can be different from person to person depending on what part of the computer blows so maybe a better question is how might I confirm or check that the ECU functioning completely?

 

Edited by cham
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Check for codes first, on the off chance the computer has some idea what's happened. If it'll communicate with the OBD scanner, you know it's getting power and it's at least somewhat functional.


I haven't diagnosed an IACV failure on an R50, but IIRC it takes out its own mosfet in the computer, and that's it. If that's all that's gone, you might get it to start if you open the throttle part-way with your foot to make up for the air it's not getting from the IACV. If it'll start and run like that, but won't idle, that supports your theory. You could also open the computer, see if it smells like fried electronics, and inspect the mosfet (I remember seeing pictures of what it looks like and where it is, but that was a while ago) for obvious signs of being fried.

 

 

I doubt the 4x4 light is related. Probably just the auto transfer case computer getting confused, especially if you have manual hubs. Unlikely that all six coil packs failed at once. Fuel pump noise is a good sign (assuming you're not just out of gas), but if you run out of things to check, wouldn't hurt to make sure you have fuel pressure. You could also pull a spark plug and see if it's wet with fuel after cranking.

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I'd check for codes first too as mentioned previously.

If your ECU died, it would have taken out a fuse/fusible link. Mine did that, but I may have shorted it. (I have a '93 though.)

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So long story short, I ended up just getting the vehicle towed to my shop because it had to get off my street anyways otherwise I would have gotten a ticket for parking violation.  I dropped by the shop today to pick something up from my vehicle and they had just started working on it.  Apparently the ecu was throwing only immobilizer codes which is quite interesting.  There is only one key I have with the vehicle and it is the original.  It wouldn't be like a low battery for the keyfob throwing off the security system by any chance would it?  Could it still be the IACV failure perhaps, and this just happens to be the section of the ecu that got damaged?  They didn't seem alarmed when I raised the IACV defect in conversation because apparently they are not strangers to it which gives me a little peace of mind.  As far as fuses go, I'm curious what you mean Cuong Nguyen by the fuses being taken out with the ecu.  What notable fuses blowing do you know of that more than likely means a donesky ecu?  

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I shorted out my ECU because I grounded out the ignition hot to the MAF which is irrelevant to your problem. It took out a fusible link in the process at the battery but did not blow any fuse in the fuse panel. 

check your wiring diagram and see how the immobilizer codes are triggered. Have you gone over the FSM?

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