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1999 Audi A4 Check Engine Light on: Code P0411


My 1999 Audi A4 2.8 V6 (only 76,000 original miles) is in great shape (I live in San Diego County, and drove to Las Vegas and back and got 30 MPG on the trip…although I did turn-off the AC).

For the last three months, the check engine light has been on (it is not flashing). I had the engine scanned at both AutoZone and O’Reillys, and both scans came-up with the same code: P0411 - Secondary Air Injection - Incorrect Upstream Flow. One of the scans also stated: Inspect for faulty vacuum hose(s) at Air Injection System.

I have no idea what this means…however, I am hoping it is something I can easily fix myself (specifically, I am hoping I only need to change-out an easily-accessed hose somewhere on the car).

I will appreciate all feedback…good news, and bad news.

The engine in your vehicle has a secondary air injection pump.

Locate this component, and check the inlet hoses/filter for this pump for proper operation.


Not trying to be mean, but if you don’t understand this, there is nothing you can easily fix. Besides it’s an Audi, nothing is easy, or cheap.

Air is injected under pressure into the exhaust system on some cars b/c it helps reduce pollutants that come out the tailpipe. Done to make the car emissions compliant. There’s hoses and valves before and after the pump, and where the air meets up with the exhaust there’s probably some kind of valve there too. Apparently this is a common problem on certain Audi models, click below for more info. Best of luck in getting the problem resolved. It doesn’t seem like it is an overly complicated problem, but whether this is something you can do yourself, don’t know. No harm to take a look in the pump area if that’s possible without removing other parts, maybe a hose has fallen off is all.