[s-cars] S6 starting problem - ECU fuse

James Murray (QA/EMC) james.murray at ericsson.com
Thu May 19 18:07:57 EDT 2005

Rich, this helps... 

I'm assuming the fuse to the ECU blows only when you try to start the car and not when the ignition is off and you reconnect the negative to the battery? 

This could be a failing POS (Power Output Stage) device... mine failed on me last year out of the blue (but I later found out I had a coil that was also failing, so I'm unsure if the failing coil caused the POS channel to degrade and fail), anyway you could have a channel in your POS that has grounded and failed... or even a coil that has failed.

Try this test: unplug both POS, insert new fuse, try starting the car (of course it won't start but you want to see if the fuse will blow), then plug in one POS (repeat test), then plug in the other (repeat test). If the fuse blows with either POS connected the it's likely the POS or a coil that has grounded... 

Here's a good way to test the POS individually:

Cheers, /Jamu.

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]
Sent: Thursday, May 19, 2005 4:12 PM
To: Bill Mahoney; 'Krasusky Paul (WQQ2PXK)'
Cc: audi s-cars list
Subject: [s-cars] S6 starting problem - ECU fuse

bill (and s-car list),

i have checked the 5 amp ECU fuse and i finally found a blown fuse,
which i was hoping was a good sign. i unhooked the neg. battery
cable, inserted a new 5 amp fuse, but once i reconnect the neg.
terminal, it blows the fuse immediately. i'm unaware of anything
i might have done to cause this situation. most of the work was
routine (including CV boot, tie rod end, new stromung exhaust,
pads, rotors, hoses...), but i also fabbed up a CAI. the MAF is
hooked up fine and nothing else seems problematic. any thoughts
on what might be blowing the 5 amp ECU fuse? honestly, i'm at
a lose.

thanks again for any help.

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