P0411 on Audi: How to Diagnose & Fix
Secondary Air Injection System Incorrect Flow Detected
1 Audi model · 1 documented issue · $80-$1,400 repair
P0411 on Audi by model: symptoms, diagnosis and fix
The 4.2 V8 in the D2 A8 (both the early 32-valve ABZ and the later 40-valve AKB/AUX/AYS/BFM) runs a vacuum-operated secondary air injection system with one combi valve per cylinder head, fed by small-diameter hard plastic vacuum lines that become brittle with heat and crack. Both banks have their own combi valve, and it is usually the hard vacuum line that goes to them that breaks and causes a vacuum leak and inoperable SAI. Owners report replacing vacuum hoses and the SAI relay only to have the CEL return, and then having to look at replacing the SAI pump (SAIP), the solenoid on top of the engine, and replacing/cleaning out the combi valves aft of each cylinder head, which involves carbon buildup in the cylinder head ports. Symptom is a check-engine light shortly after a cold start with P0410 (or banked variants P0491/P0492).
Common Symptoms
- Check engine light after cold start
- Audible hissing from engine bay at cold start
- Rough idle for first 30-90 seconds after cold start
- Failed emissions/smog test
- Pump noise (whining) on cold start
How to Fix
Diagnose by starting the engine cold so the SAI system runs and listening for the vacuum leak, then looking around for the crack. Sticky/partly opening combi-valve or slow running pump are all candidates — you can spin the pumps up using VCDS output tests to verify pump current draw. Replace brittle vacuum hose with silicone, test combi valves with a hand vacuum pump (they should hold vacuum and audibly click open), and if codes persist with new vacuum/valves the SAI ports in the head will need to be carbon-cleaned. The pump itself (smog pump) typically fails when a leaking combi valve allows exhaust moisture to back-feed and corrode the impeller.
Sources for this issue (1)
P0411 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0411 mean on a Audi?
P0411 stands for "Secondary Air Injection System Incorrect Flow Detected." This emissions code means the secondary air injection system is flowing an incorrect amount of air. That system pumps fresh air into the exhaust shortly after a cold start to help the catalytic converter heat up and burn off pollutants faster. The computer monitors the resulting change in exhaust oxygen readings, and sets this code when the measured airflow is too high, too low, or otherwise not what it commanded. It is primarily an emissions issue and often traces to the air pump, valves, or their plumbing. On Audi it is documented across 1 model: A8.
What are the most common causes of P0411?
The most common causes of P0411 are: Failed secondary air injection pump, Stuck or faulty air switching/check valve, Carbon or moisture clogging the air passages, Leaking, cracked, or disconnected air hoses, Faulty pump relay or electrical wiring, Damaged or corroded connectors, Faulty vacuum control solenoid for the system. The specific cause varies by vehicle.
How much does it cost to fix P0411 on a Audi?
Published repair estimates on Audi range from $80 to $1,400 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0411 on a different make?
View P0411 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.