[s-cars] S6 starting problem - ECU fuse

Paul Gailus gailus at mindspring.com
Thu May 19 23:23:00 EDT 2005 

Unfortunately, I'm tending to think that Mark could be right
about a fried ECU, especially if you used a boost charger to
start the car.  If the battery was "sulfated" (causing a relatively
high source impedance) or the battery connections were bad,
then there could have been some high peak voltages at the ECU
with a boost charger.

It's possible that there could be a 5 volt regulator or similar
device connected to pin 18 of the ECU that failed with a
short directly to ground. In this case just the regulator would
need to be replaced. However, if the failure propagated beyond
this point then it might get more messy to repair.

Just as I'm writing this, I just saw Feico's post pop up.
It sounds like he's seen this before, so I'd recommend that
you contact him about it.

Paul


----- Original Message -----
From: Mark Strangways <Strangconst at rogers.com>
To: James Murray (QA/EMC) <james.murray at ericsson.com>; 'Rich Beebe'
<rich at beebecomm.com>; Bill Mahoney <wmahoney at disk.com>; 'Krasusky Paul
(WQQ2PXK)' <WQQ2PXK at ups.com>
Cc: audi s-cars list <s-car-list at audifans.com>
Sent: Thursday, May 19, 2005 7:43 PM
Subject: Re: [s-cars] S6 starting problem - ECU fuse


RE: [s-cars] S6 starting problem - ECU fuseIf it where me... and thank god
it isn't...
I would pull the ecu out, open up the cover and look for signs of carnage.

That to me is the simplest first approach.
After that, I would be getting some schematics of the out board connection
to the ECU and verify Gnd is where GND should be and that outputs don't bias
heavily toward ground.

Remember that the voltage to the ECU with ignition off is there to maintain
the adaptive tables. So therefore it just points to a smoked ecu ! Hope I am
wrong as I usually am :-)

Mark
  ----- Original Message -----
  From: James Murray (QA/EMC)
  To: 'Rich Beebe' ; Bill Mahoney ; 'Krasusky Paul (WQQ2PXK)' ; Mark
Strangways
  Cc: audi s-cars list
  Sent: Thursday, May 19, 2005 7:35 PM
  Subject: RE: [s-cars] S6 starting problem - ECU fuse


  Rather than think negatively... (as in blown ECU)... let's think positive
that you have a shorted wire in the cabling due to your recent engine work?
disconnecting the POS anyway and start tracing the wires from the ECU fuse
and start testing each point...



  -----Original Message-----
  From: Rich Beebe [mailto:rich at beebecomm.com]
  Sent: Thursday, May 19, 2005 7:30 PM
  To: James Murray (QA/EMC); Bill Mahoney; 'Krasusky Paul (WQQ2PXK)'
  Cc: audi s-cars list
  Subject: Re: [s-cars] S6 starting problem - ECU fuse



  i disconnected the battery after the 1st fuse blew when i tried to
  put it in. doesn't make a difference - this thing is blowing fuses
  no matter what the configuration.

  rich

  > From: "James Murray (QA/EMC)" <james.murray at ericsson.com>

  > Well you can try (easy to pull the connectors off the POS)... if I
remember
  > correctly the fuse did not blow until I tried to start the car, meaning
I kept
  > replacing the fuse (many times) until I pulled the POS connectors, but
the
  > fuse would only blow when I tried to start the car... now my memory
might be
  > foggy on this... but I think that's how it went. Then again I never
  > disconnected the battery negative either...
  >
  > /Jamu.
  >
  > -----Original Message-----
  > From: Rich Beebe [mailto:rich at beebecomm.com]
  > Sent: Thursday, May 19, 2005 7:18 PM
  > To: James Murray (QA/EMC); Bill Mahoney; 'Krasusky Paul (WQQ2PXK)'
  > Cc: audi s-cars list
  > Subject: Re: [s-cars] S6 starting problem - ECU fuse
  >
  >
  > actually, it's blowing the fuses without even starting the car,
  > just by connecting the battery.
  >
  > i wonder if it would help to disconnect the POSs and attempt the
  > fuse again? i've already checked the coil wires for a short and
  > the ground - all seem fine. i'm gonna need more 5 amp fuses.
  >
  > i thought for sure, when i saw a blown ECU fuse, that it blew
  > because of the jump-starting. now, when it blows a fuse every
  > time the battery is hooked up, i can't believe it's something
  > else - knowing it was running just the other day with nothing
  > different. so strange.
  >
  > rich
  >
  > From: "James Murray (QA/EMC)" <james.murray at ericsson.com>
  >
  >> 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:
  >> http://forums.audiworld.com/a4/msgs/1594531.phtml
  >>
  >> 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.
  >>
  >> rich
  >> _______________________________________________
  >> S-CAR-List mailing list
  >> S-CAR-List at audifans.com
  >> http://www.audifans.com/mailman/listinfo/s-car-list
  >>
  >
  >
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