Join Now
International Automotive Technicians Network
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

Files Referenced:


17 Replies Received (View Replies)


car Vehicle Data

1999 Audi A6 Quattro 2.8L

Engine2.8 L
Trans5-speed Automatic (Electronic)