The car: 2000 A4 1.8T Q, engine = ATW, 91,000 miles, chipped + forge DV, paper element air filter is very clean (K&N coming soon).

Problem: trouble code P0411, incorrect secondary air flow...from Autozone's scanner.

Last weekend, I fixed the plumbing going from the air cleaner box to the secondary air pump and from the air pump to the combination valve. One tube was loose at the pump and the other had a big crack in it.

The check engine light did not go off, so I stopped at Autozone on Friday...same code P0411.

Yesterday, I checked the plumbing again, made sure connections were tight and I checked the vacuum hoses to make sure there weren't any obvious leaks. I clipped the ends off all of the vacuum hoses (for the AIR system & DV) and put them back on. I cranked up the engine (cold) and the secondary air pump ran for about 1 minute, shut off and engine revs dropped from fast idle to normal. Then about 1 minute later, the secondary air pump came on for about 5-10 seconds & shut off. The outside air temp was about 45 degrees and this was all done at idle. The air pump sounded okay...like a quiet vacuum cleaner and I could feel it hum/vibrate.

Question: Is this normal secondary air injection system behavior? Any bets on whether or not the Check Engine Light goes off in a couple of days? If not, what should I check next?

Thanks,
Larry

 

You need a vag com to clear the CEL light, then you will be able to tell if your repair worked.

 

I was told that the CEL will go out in 2-3 days IF the fault has been corrected. Is that incorrect?

Thanks for your reply.

--Larry

 

I had the same problem forever. There's a valve (silver cylinder) back by the firewall. There's also a solenoid mounted under the intake manifold. The culprit in my car was a vacuum hose at the valve. It had been ripped off, presumably when i changed the O2 sensor.