[s-cars] Status of "Blown ECU Fuse"

James Murray (QB/EMC) james.murray at ericsson.com
Mon Apr 26 12:30:29 EDT 2004

Well that "now running fine" didn't last long, although this time I got lucky because the car failed in the parking lot at work on Friday night, but this time it was for good! So armed with my tools I went back on Saturday morning and proceeded to swap out the bad coil... got the job all done, went to fire her up and pop... there goes the fuse again! what the heck?  Turns out the PSO or POS (whatever you want to call it) had not blown a channel but it must have fused a channel :-( crap... talk about bad luck :-(

Anyone have a source for new PSO/POS at a good price? (Yes I know about the spare channel available in the PSO/POS).

So if this happens to you, don't just suspect the coil, the PSO/POS could be at fault too. 

Cheers, /James.

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]On Behalf Of James Murray
Sent: Friday, April 23, 2004 11:15 AM
To: 'Igor Kessel'; s-car-list at audifans.com
Subject: RE: [s-cars] Help! Blown ECU fuse (what are the probable causes
I should inves tigate?)

Thanks Igor... but I changed the fuse in the parking lot and all is running fine again? Although this could explain why! and maybe one of the coils is on it's way out... I've got a fresh set waiting to go in with new plug boots, but never got around to installing them, well that's my mission for Saturday morning !

Any other possible causes guys?

Cheers, /James.

P.S. I still say it's a crazy place to locate that fuse! what a frustrating place...

-----Original Message-----
From: Igor Kessel [mailto:kbattpo at verizon.net]
Sent: Friday, April 23, 2004 11:03 AM
To: James Murray (QB/EMC)
Cc: s-car-list at audifans.com
Subject: Re: [s-cars] Help! Blown ECU fuse (what are the probable causes
I should inves tigate?)

James Murray (QB/EMC) wrote:

> Paging all guru's and BTDT... any advice for tracking down the cause of a blown ECU fuse? I'll keep searching the archives but so far I came up empty. My car is a 93 S4. 
> Yesterday (during the day), while in reverse the car suddenly died, tried restarting multiple times... nada. Scrambling to get her out of the way of blocking traffic I slightly cracked my rear middle driver side tail light in the process... don't ask it was a really really dumb ass move on my part (brain fart I guess), anyone have a replacement they could sell me? Anyway, car turns over fine, everything appears to work, but she wouldn't start!? So the possible causes start to run through my head as I sat there stranded... 
> Checked all fuses on driver's side (maybe it's the fuel pump), nope all are ok. A little low on gas, maybe the remaining gas is bad? - not likely as it should at least run rough, run to get a fresh can of gas anyway just to be safe, nope didn't work.  Ok time to check for a spark, pull the coils out and low and behold there's no spark! Ok what could cause this I thought... Camshaft Positioning Sensor - oh crap not this again I thought, but damn it I replaced that 1.5 years ago... ok re-set the plug anyway just to be safe... grab a piece of wire to pull to activate the codes and start  reading the check engine light. Hey wait a minute there's no check engine light... that's strange ! Ah damn the thing must have burnt out. Of course it wasn't after a lot of frustration that I realized it was too much coincidence that the check engine light burnt out, so I started from there... luckly I was close enough to walk to the office and search on SJM site (hmmm look at that the ECU i
s !
>  fused). I pulled the carpet out and low and behold the damn ECU fuse had blown !!! what the hey? what could have caused this? 
> Is it possible there's a pinched wire someplace? I recently had the front bearings and tie rods changed and I changed the driver door handle cable replaced, so I had the driver side door apart. I can't think of anything that could cause this with respect to the very recent repairs, but you never know. 
> Thanks for listening... 
> Cheers, /James.
> P.S. What was Audi thinking putting a fuse in a location you can't check, and have to cut the carpet to get to it... of course it's not suppose to blow, but that's what fuses are for... just in case! 
> BTW: So I know how to check for spark on these cars, how do you check if you have fuel delivery if stranded? (for future reference)
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one of the coils has shorted its primary to GND. Check the archives on 
for a lengthy thread on the subject "sumbling, stalling, dead" by Stefan 
Richter and my post on fusing the coils individually.

Igor Kessel
two turbo quattros in the stable,
the third one is in the works
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