iamrph

I own a 1999 A6 quattro with 224,000 miles on the odometer. A few months back a check light came on and the P0411 code was the culprit. It also had the knocking sound the first 15-20 seconds after I started the motor. I ordered an air pump and had my mechanic put it on. Problem solved I thought, but I was wrong! It turns out the pump I ordered off eBay wasn't an exact fit and I still had a knocking noise 15-20 seconds after starting.

I ordered another pump from a different supplier on eBay and again my mechanic installed it and cleared the code. Thre next morning I started the car and thought my problems were solved because the grinding noise stopped and the check engine light went off. I drove to work and because I was running late I had to drive faster than normal (120mph top speed). That evening after work when I started the vehicle the check engine light came back on and this time instead of a knocking noise there was a whining noise. This time instead of lasting 15-20 seconds and sounding like a grinding or knocking sound, this sound was different. Almost like a whining sound that lasted for 1 minute and 12 seconds. I told my mechanic and he said it sounded like one of the hoses came off the air pump. I stopped mby and he checked it out and says everything was hooked up properly and he cleared the code.

When I sorted it up no noises and the check engine light didn't come on. I was hoping all was well and I drove home. I drove about 15 miles and stopped at a red light. Then, while I was idling I heard the whining/whirling of the air pump & the check engine light came back on! I thought to myself "Self, what's the chances you got 2 bad pumps off eBay (the 1st came from Michigan and the 2nd from California). I stopped at O'Reiley's Autoparts and had the code read. P0411 was what came up. My thoughts were to order the part from O'Reilly's until I was quoted $499 for the pump! Could it be something other than the pump causing the code? I'm not having any luck replacing the pump. What should I do next?

georgeb944

With VCDS, you can run an output test that will operate the SAI pump to see if it is working properly.

Here is the Ross Tech wiki on P0411

16795/P0411/001041 - Ross-Tech Wiki