i have a 99 A4 2.8 Quattro im gettin a CEL the code showing is P0411. Need some help, does any1 know what cause is thanks for the help.

 

It sounds like your Secondary Air pump is failing. This could also be caused by a broken air hose or vacuum line to the secondary air pump. Check the operation of the combi-valve.

 

There's a chance it could be the relay as well. The stock relay is cheap and as far as I've seen quite notorious for getting sticky and not opening up when its supposed to. Its an easy check, the relay is (unless the 99 changed this from the 98) in the enclosure with the ECU, its the only other thing in that black box besides the ECU so you cant miss it. Unplug it for a few minutes and plug it back in, drive about 20 miles and see what happens. If after you've checked all the hoses and combi valves its still having an issue, replacing the relay will be the cheapest thing before having to completely replace the pump itself if that's what is faulty.

Good luck

 

Thanks for the help, but how can i check if the Secondary air pump is failing and where is located same with the combi valve, Combi valve is it the small thing which has 2 pipes connected to it on either end, on top of the air box. Mine makes a clicking noise at times and keeps increasing.

 

Thanks for the help, but where is the ECU located sorry stupid ? just starting to get familiar with the A4's.

 

The ECU is inside a black box about the size of a couple phone books stacked together on the drivers side of the engine bay right below the windshield. The cover is bolted on with five 8mm screws which are all easy to get off except the one located at the back, that one's a little more tricky but not impossible if you have a 1/4 inch drive ratchet and small hands.