DTC P0411 Volkswagen, Audi, Skoda and SEAT (P041100): Secondary Air Injection Incorrect Flow, Causes and Fix

DTC P0411 Volkswagen, Audi, Skoda or SEAT (P041100, VCDS 16795, often typed po411) means the engine computer switched on the secondary air pump after a cold start and did not see the extra air reach the exhaust. The car drives normally, because the system only runs for about a minute after a cold start, but the light stays on and the car fails an emissions test. The cause is usually a cracked hose or vacuum line, a blown 40 amp pump fuse, a stuck combi valve or a pump full of water, in that order of cost. First check: start the car cold and listen for the pump.

Can I Drive With a P0411 Code?

Yes. The secondary air system only works for the first minute after a cold start, so P0411 changes nothing about how the car starts, idles, pulls or uses fuel. You can drive it for as long as you like.

If your car hesitates, idles rough or stalls, that is a different fault. Scan for other codes before you touch the air pump.

The deadline is the emissions test. A lit light fails the OBD inspection in every US state that runs one, so the code has to be gone and the readiness monitors complete before you go, and until then the light hides any new code that comes along. In the UK a lit engine light fails the MOT on cars first used from July 2003, but many UK and EU petrol VWs and Audis built after about 2005 have no secondary air pump at all. VW fitted it for US emissions rules, which is why most cars with P0411 are 1.8T and 2.5 models sold in North America.

What Does the P0411 Code Mean?

P0411 means the air pump was told to run and the computer saw no flow. For about 30 to 90 seconds after a cold start the engine runs rich, so an electric pump blows fresh air into the exhaust ports through a vacuum-operated combination valve, the combi valve, where the unburnt fuel burns off and the catalytic converter warms up in seconds instead of minutes. On the 1.8T, the 2.0, the 2.7T and the V6 the computer watches the front oxygen sensor, which should read lean while the pump runs. On the 2.5 from 2005 it watches a pressure sensor in the hose between pump and valve. No change at the sensor, P0411.

The code stored next to it narrows things down. P0491 is insufficient flow on bank 1, which the 2.5 and the V6 store instead of, or with, P0411. P0418 is the pump relay circuit. P2431, P2432 and P2433 are the 2.5’s pressure sensor, and VW has a bulletin for them (below). P1411 and P1423 are older VW-only secondary air codes that mean the same thing.

What Causes a P0411 Code on a VW or Audi?

Seven things cause P0411 on these cars. Cheapest and most common first; the order is my reading of VW’s bulletins and the owner reports, not a survey, and Ross-Tech’s list for 16795/P0411 names the same parts.

Check the fuse and the vacuum lines before you buy anything. The pump is the dearest part and the least common cause.

1. A cracked or detached vacuum line to the combi valve. Thin plastic at the back of the engine. No vacuum, the valve never opens. An A4 B5 owner found his “completely rotten off”. Under $20.
2. A blown 40 amp pump fuse. On top of the battery or under the plenum cover, not in the dash box, which is why people miss it. One owner bought a pump, a valve and a hose before a dealer found it: $29.50.
3. A split pump hose or a loose end. The corrugated hose from the pump; the air escapes before the valve. Under $40.
4. A stuck combi valve. Corroded shut by exhaust condensation. A 2002 A4 owner pulled vacuum on his and nothing moved. $60 to $140.
5. A dead pump. Water that came in through a leaking combi valve seized it. You hear it: grinding or whining at a cold start, or silence. $120 to $450, plus the valve.
6. A leaking turbo bypass valve, part 06A 145 701 N. Outside the system, but it shares the combi valve’s vacuum supply, and a Vehicle Service Pros tech tip from May 2017 says it can stop the valve opening. $30 to $60.
7. The N112 solenoid, the pump relay J299, or the fuel pump relay J17 that feeds it on some cars. Rare. The output test in step 3 proves all three.

P0411 on the Jetta and Golf 2.5

Jetta and Golf 2005 to 2014, Rabbit, New Beetle from 2006, Passat 2.5. The same seven apply, with two differences. The combi valve is electric, and VW’s Tech Tip 26-12-01 says to test it with the output test before anything else and replace it if it does not move through its full range. And there is a pressure sensor in the hose that sets P2431, P2432 or P2433 when it fouls; VW bulletin 2028415 covers it. Both are in the fix section below.

How to Diagnose a P0411 Code in Six Steps

Listen at a cold start, check the fuse and relay, run the output tests, check the hoses, test the combi valve, tip the pump. Most cars are solved by step 3.

1. Start it cold and listen

With the engine stone cold, start it and stand by the engine bay. The pump sounds like a small vacuum cleaner for about a minute. A pump you can hear means the fuse, relay and motor are fine and the air is escaping somewhere, so skip to step 4. Silence sends you to step 2. Grinding, rattling or whining means the pump is dying; go to step 6, and plan for the combi valve as well, because the water that killed the pump came through the valve.

2. Check the 40 amp fuse and the relay

Find the high-current fuse for the pump in the fuse holder on the battery or under the plenum cover, not the dash panel.

A blown fuse is a fix once and a warning the second time: a pump that blows a new 40 amp fuse is drawing too much current and is on its way out.

The pump relay (J299, relay number 373 on the A4 B5) sits in the relay panel; swap it with an identical relay to test it.

3. Run the output tests

This is what a workshop does first, and it answers most of the diagnosis in two minutes. Idle the engine briefly, switch off, turn the key to on, connect VCDS or OBDeleven (output tests need the PRO plan), open the engine module and run the output tests. The pump test proves the fuse, the relay and the motor, and lets you hear any leak. The N112 test proves the solenoid, the vacuum supply, and that the combi valve opens and closes. To run the tests again, start the engine for a moment and switch off. A generic OBD2 app and a Vgate read and clear P0411 but cannot command the pump.

4. Check every hose and vacuum line

Pump to combi valve: the corrugated hose, both ends pushed home and clipped. Combi valve to N112 to the vacuum source: the thin lines, which crack where they bend and where they meet the plastic elbows. While you are there, pull the line off the turbo bypass valve (06A 145 701 N on the 1.8T) and test it with a hand vacuum pump; if it will not hold, it is bleeding the combi valve’s supply.

5. Test the combi valve

With the vacuum line off the valve, pull vacuum on its port with a hand pump. The diaphragm should move toward the pump and the valve should open; blow through the air side and feel it pass. A valve that will not move is corroded shut.

6. Take the pump out and tip it

Two or three bolts and two connections on most cars. Tip it over a tray and spin it by hand; a rough or seized motor is finished.

Water in the old pump means the combi valve has been leaking back into it. Fit the valve with the pump, or the new pump dies the same way.

How to Fix P0411

Fix the part the test found. Engine cold for all of it.

Vacuum lines and hoses

1. Trace the thin line from the N112 solenoid to the combi valve and back to the intake.
2. Cut new line of the same bore for every hard, cracked or loose section, and replace any cracked plastic elbow. Do them all at once.
3. Push each end fully on.
4. For the corrugated pump hose: spring clips off, old hose off, new hose to its stops, clips on. Check the hose from the airbox to the pump the same way.
5. Bypass valve (06A 145 701 N): one hose clip and two vacuum lines off, new valve on.

Fuse and relay

1. Fit a new 40 amp fuse of the same rating in the holder on the battery or under the plenum cover.
2. Run the output test or do a cold start.
3. If the fuse blows again, stop. The pump is drawing too much current; replace the pump before another fuse.
4. Relay (J299, number 373 on the A4 B5): swap it for an identical one in the relay panel. If that fixes it, buy the relay.

Combi valve

1. Find it: back of the head against the bulkhead on the Audis, exhaust side of the head on the Golf and Jetta.
2. Pull the vacuum line and release the air hose clip.
3. Soak the two or three bolts with penetrating oil, undo them and lift the valve off.
4. Scrape the port face clean. If the passage behind it is carboned, clear it with a wire and carb cleaner.
5. Fit the new valve with a new gasket, reconnect the hose and line. Do not bother cleaning the old valve; it rarely frees.
6. On the 2.5 the valve is electric: one connector, two bolts, same gasket rule.

Pump

1. Find it: in the engine bay on the Golf and Jetta, behind the front bumper on the A4 and Passat B5.
2. Unplug the connector, release the clips on the inlet and outlet hoses, undo the two or three mounting bolts, lift the pump out.
3. Tip it over a tray, as in step 6.
4. Fit the new pump, hoses to their stops, clips on, connector in.
5. Fit a new fuse if the old pump took one with it.

On the 2.5: pressure sensor

1. Sensor only failed: replace the sensor, part 07K 906 051.
2. Hose damaged: fit service kit 07K 198 125, a new hose with the sensor and an adapter harness.
3. The kit needs the air cleaner housing and the throttle body off to get the hose out; clip the adapter harness in on reassembly.

Confirm the fix

1. Clear the code.
2. Leave the car overnight, start it cold and listen: the pump runs and stops within about a minute.
3. Run the output tests again and watch the valve open.
4. With VCDS: Basic Settings group 077 (078 for bank 2 on the V6 and 2.7T) runs the secondary air test on a warm, idling engine and reports “Syst. OK”. That sets the readiness monitor without cold starts; the procedure is in Ross-Tech’s readiness pages.
5. Without VCDS: a few days of cold starts complete the monitor. The code must not return.

For an inspection the monitor has to show ready. Do not clear codes the night before the test.

If P0411 comes back

A week or two after a new pump: either a leaking valve has filled the new pump with water, or the pump was never the fault. Every owner on the Audizine thread who replaced parts in the wrong order ended at the fuse or a vacuum line. And if the readiness screen says the secondary air test is complete while the light is still on, the monitor says the test ran and the light says it failed; both are true until the cause is fixed.

Can I Fix P0411 Myself?

Most P0411 fixes are home jobs: the vacuum lines, the pump hose, the fuse, the relay, the bypass valve, the N112 solenoid, and the combi valve and pump on a Golf or Jetta, where both are reachable from above with hand tools. The parts are cheap, the fault is nearly always visible or audible, and a scanner with output tests turns the diagnosis into a half-hour test.

Use a garage for the pump on an A4 or Passat B5 if you have no ramp, because it lives behind the bumper; for a wiring fault, when the output test shows no power at the pump with a good fuse and relay; for the 2.5’s pressure-sensor hose, because the throttle body has to come off; and for any car where the code returns after the obvious parts are new.

Ask the garage for the output test result and the vacuum test on the valve, not a parts list.

P0411 With Other Codes

P0171, system too lean, arrives with P0411 on the 1.8T because a cracked secondary air vacuum line or a broken pump hose is also a vacuum leak, and the lean code often shows up first. Fix the leak and both codes go. The P0171 page covers the other 1.8T leak points.

P0491 or P2431 to P2433 on a 2.5 mean you start with VW’s combi valve output test and the pressure sensor bulletin above, not the pump.

P0418 is the pump relay circuit itself: fuse, relay and the wiring to the pump.

P0420 or an oxygen sensor code next to P0411 does not mean the catalyst is damaged. Fix P0411 first, clear everything and see what returns; the P0420 page explains what P0420 needs before you believe it.

A secondary air delete sets P0411 on every cold start unless the software is changed, and a car with the system removed fails any inspection that reads the OBD port. Where the car is tested, the delete is not a fix.

P0411 Cost to Fix

Fixing P0411 costs $10 to $450 in parts and one to two hours of labour, and most cars need the cheap end. US prices from FCP Euro and ECS Tuning, UK prices from Euro Car Parts and Autodoc.

Labour is one to two hours at an independent, $100 to $250 or £80 to £180. The diagnosis is one output test, so a quote of several hundred for “diagnostics” is the moment to ask what was tested. A dealer pump and valve together on a 1.8T can pass $700 fitted.

Three things are not worth paying for until a test says so. The pump, because it is the dearest part and the least common cause. The front oxygen sensor, because a sensor that reads correctly the rest of the time is the witness, not the fault, and a failing one sets its own code and shows its own symptoms. And the catalytic converter, because P0411 does not mean a dead catalyst.

FAQs

Last Updated: October 2026

Ayush Sondhi

Founder of TheCarLane | Automotive Enthusiast
Ayush shares practical automotive knowledge based on real-world ownership and hands-on experience. His work focuses on diagnostics, engine systems, common car problems, and clear explanations that help everyday drivers understand their vehicles better.