12v-V6 codes and engine check light.

Fri May 25 11:58:41 EDT 2007

Had this 1995 A6 Quattro sedan for a year and a half now.  The engine
check light comes on at some point everytime I drive any distance.  No
change in performance.  When pulling the codes with Vag-Com, I get an
EGR related code. 

Here is what I have done.

1.  Completely cleaned the passage into the intake manifold from the
EGR.  I even went so far as to pull the manifold off and clean it out
some as well.

2.  Verified EGR is holding a vacuum by using a 30cc syringe and some
tubing.  Pulled the plunger back and could here the EGR click closed and
it would pull back the plunger.  So its definitely holding a vacuum.

3.  Verified the solenoid on the passenger side wheel well that controls
the canister and the rest of the recovery circuit.  I forget the correct
name for it but there is a checkout procedure in the service manual.
1st step is hooking up a test light and turning the motor over while
connected from GND to one of the pins verifing power is getting to the
solinoid,  the 2nd part of the test involves some test adaptors that I
don't have and verifying the wiring back to the ECU.  I physically
followed the wiring back to the ECU and it looks to be in good shape.

The last thing left in the troubleshooting is replacing the ECU.  Anyone
else ever had to change out an ECU just for a repetitive EGR error code?
Any other thoughts as to what might cause it?  I don't have the exact
code right now, but when I get home today I can pull it again and post
it.

Also, is there any problem with switching an ECU from the same year A6
for testing purposes?  My wife has a 95 A6Q wagon as well so it's the
same ECU I believe, I just would have to verify part numbers, but I can
swap it over and take mine for a drive and see if that does solve it.  I
just am wondering with her car being an automatic if there are some
settings or anything stored in the ECU that's specific to a particular
car.  Or is it just as easy as in the type 44 where you took the old ECU
out, and put a new one in?

What are the effects of the EGR system not functioning correctly?  The
car has passed emissions, so it obviously wasn't a huge factor there.
My milage is about 22 mpg from week to week with my commute being almost
all on the highway at about 75-80 MPH.  Is that avg for this car?  It's
a standard btw.

Just kinda tired of the check light and I would like to get it to stop
coming on without taking the bulb out :P

Thanks!

Rob Beatty

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