[s-cars] Re: 95.5 S6 Keeps Blowing 5Amp Fuse Near ECU

[Steve Eiche]

Chris,
FWIW, I have repaired two dead AAN ECUs that were damaged by jump
starting.  Both blew fuses.  The good thing is both were repairable.
One was damaged by a tow truck jump start, the other by a battery
charger in the "boost" mode.  The problem is these boosters, especially
cheap ones, can put out high voltage spikes that can/will damage the
circuits in the ECU meant to protect the circuitry from high voltage.
These components break down and short circuit to ground which cause the
fuses to blow.

As for trouble shooting, I highly doubt that you suddenly have a short
to ground somewhere in the harness after just sitting.  You can test
where the problem is quite simply.  First, pull the fuse in question and
measure the resistance with a DVM on the fused side (no voltage with
fuse pulled) to ground.   You will likely see close to 0 Ohms.
Disconnect the components on that circuit one by one.  Measuring the
resistance to ground after disconnection each component.  The offender
will be very obvious this way.  (I would put the meter in continuity
"beep" mode and disconnect items until the beep stops.) If everything is
disconnected and it still shows a short to ground, the problem is in the
harness.  This is very unlikey IMO/E.

Steve Eiche
Shade Tree Software, LLC
shadetreesoftware.com
seiche at shadetreesoftware.com





Another incremental progress. According to Bentley, the fuse that is
blowing is a 5amp fuse that belongs to the injectors. It is located in
red plastic housing on position 5 of the "Electronic Box" according to
Bentley.

It is on pages X804 and X805 of Volume 3 of Bentley. It corresponds to
N30, N31, N32, N83 and N84.

I'll be trying to find these circuits in the Bentley. I "think" it's
safe to say the ECM is safe and whatever is blowing the injector fuse is
what is keeping the car from starting.

Any help to help me solve this would be EXTREMELY apprecaited. This
whole trek has been very educational for me.

Chris