P0455 Gross Leak 1999 Audi A6 Quattro
Posted to Technical Tips Forum on 12/21/2011
17 Replies
Hi TTiF,
I recently had a customer come into my shop with a vehicle
that failed it's bi-annual Smog Inspection. The vehicle
failed the OBDII Functional Test for a lit MIL and a P0455
Evaporative Emission System Gross Leak.
There aren't a lot of Volkswagens or Audis in my
neighborhood, and this is the first EVAP failure I've ever
done on this type of platform.
I started by verifying the integrity of the gas cap with my
Stant gas cap tester. It uses pressure to test the cap,
which is good since the Audi uses a Leak Detection Pump to
test the EVAP system for leaks. The gas cap tested good.
The next step I took was to run Basic Setting 070 and 071
with my ProDiag Palm Scanner. It passed the 070, but failed
the 071.
To me the obvious thing to do next is to look for a leak in
the gas tank and canister. I isolated the tank and canister
from the purge and vent hoses, put my flow meter on the
filler neck and found no leak. That was a lot of work for
nothing.
I looked in the iATN TechHelp Archives and I found a
response that said to pinch the hose coming from the
Canister Purge Control Valve and run Basic Setting 071. If
it passes the test, you've found your bad component that
caused the P0455 to set. I went back into the
archives, but I couldn't find the response to give the tech
credit for this tip.
[1999 Audi A6, Emissions Photo]
It worked. I replaced the Canister Purge Control Valve, ran
the 071, the light went out. I performed the Smog Inspection
and issued a certificate.
Danny from California
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