Emissions control: EGR, DPF, catalytic converter and AdBlueGeneric OBD-II codeUrgency: Monitor
Code P0411: secondary air injection: incorrect flow
What code P0411 means
The ECU has found that the air the secondary air injection pump pushes into the exhaust after a cold start does not match what it requested: either too little air arrives, or too much of it continuously.[1][2]
This system only works for a few seconds after starting with a cold engine. It injects fresh air into the exhaust manifolds so that unburnt fuel is burned off and the catalytic converter reaches its operating temperature sooner. That is why the fault often only reappears after a whole night with the engine cold.[1]
It is a generic code (it starts with P0), but only some petrol engines have this system; on other cars you will never see this code.[1]
Original definition (SAE J2012): Secondary Air Injection System Incorrect Flow Detected[1]
Causes of P0411
From most to least likely, according to the sources.
- 1Faulty or seized secondary air pump, often due to moisture and internal corrosion or brush wear at high mileage.[1][2]
- 2Switching or combination valve stuck open or closed.[1][2]
- 3Air hoses or pipes blocked, cracked or disconnected, or corroded non-return valves.[1][2]
- 4Passages to the exhaust ports blocked by carbon deposits or condensation.[1]
- 5Electrical fault: pump relay or fuse, wiring, or a faulty air pressure or flow sensor.[1]
Symptoms
- Engine warning light on, often shortly after a cold start.[1][2]Engine warning light: faults that cause it
- Higher emissions and a possible MOT failure when they are measured.[1]Pollution control faulty: faults that cause it
- Slightly uneven or high idle during the first minute after a cold start.[1]Vibrations: faults that cause it
How to diagnose P0411
In order: from the most likely and cheapest to check to the most expensive.
- 1Read all codes and the freeze-frame data: see whether there are valve circuit codes alongside this one (on some Toyota V6/V8s, P0412 or P0416 to P0418).[1]
- 2With the engine cold, activate the pump with the diagnostic tool or do a real cold start and listen: if it makes no noise it may be the pump, the relay or a fuse; if it runs non-stop, the valve may be stuck open.[1][2]
- 3Inspect hoses, pipes, the switching valve and non-return valves: cracks, rust, soot and accumulated water.[1][2]
- 4Measure the pump's current draw with a clamp meter and check the relay, fuse and wiring.[1][2]
- 5Replace the pump only if it is seized; if passages are blocked, clean them and replace the non-return valves.[2]
Can I keep driving with P0411?
Monitor
Sources agree that it is a cold-start emissions fault: the car behaves normally with a warm engine and can be driven. The light will stay on and you are likely to fail an emissions test until it is repaired.[1][2]
Documented faults related to P0411
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Engine sensors: the most serious faults by engine and car
- High severityFrequency: Occasional2.0 DTI and 2.2 DTIVP44 injection pump and air mass meter failureGerman Wikipedia documents recurring failures of the Bosch VP44 injection pump and the air mass meter in the early years of this engine. An owner testimony for this engine describes the pump being replaced at 192,500 km, at a cost the owner calls «prohibitive».
- Medium severityFrequency: Common2.0 TDIClogged particulate filter or faulty pressure sensorThe 2.0 TDI's particulate filter clogs if the car mostly makes short journeys, because it never gets to regenerate; sometimes the fault is just the differential pressure sensor. Cleaning it costs around €200 and replacing it, €800 to €3,000.Repair (garage): €800–€3,000
- Medium severityFrequency: Common1.4 and 1.6 8vCrankshaft position sensor failure (TDC sensor)The crankshaft position sensor (capteur PMH, or TDC sensor) appears repeatedly in the reliability sources for the Clio II, the Kangoo I and the Dacia Logan I with this engine, with hard cold starting or stalling as the main symptoms. It is a cheap part, but the failure can leave you stranded.
- Medium severityFrequency: Common1.4 and 1.6 16vCrankshaft position sensor failureThe crankshaft position sensor (capteur PMH) appears repeatedly in the reliability sources for almost every generation with this engine, with hard cold starting, stalling or the car cutting out unexpectedly. It is a cheap part, but the failure can leave you stranded.
Wiring, connectors and short circuits: the most serious faults by engine and car
- Critical severityFrequency: OccasionalBMW N62 / N63Additional turbo coolant pump with a risk of short circuit and fireIn 2011 BMW recalled 5, 6 and 7 Series, X5 and X6 models built between 2007 and 2011 because of the additional turbo coolant pump: moisture, a short circuit and, in extreme cases, a fire. In 2012 there was another campaign for a crack in the pump, with a more robust version.
- High severityFrequency: Occasional1.3 TCeBlown fuel pump fuseOn the Renault Captur II and Clio V with the 1.3 TCe engine, a 20-amp fuse can blow and leave the car without an engine. According to L'argus, in April 2021 this fault still had no factory fix; the official service centre's diagnosis includes checking, and sometimes replacing, the catalytic converter.
- High severityFrequency: OccasionalM264/M254Poorly tightened 48 V earth wiring in the mild-hybrid system (fire risk)Mercedes-Benz has issued several recalls (2022-2025) because the 12 V and 48 V earth connections of some cars with a 48 V system may be poorly tightened: resistance rises, the connection heats up and a fire cannot be ruled out. The official workshop checks them and repairs them if necessary in an hour or more.
- High severityFrequency: Occasional1.9 TDIUnit injector tappet wear and injector wiring damageOn the unit injector system, the tappets that operate the injectors can wear if the oil is not changed on time, and the injector wiring can be damaged by contact with oil, causing misfires or loss of power.
- Critical severityFrequency: CommonRover 75Seat SRS connector fault with airbag and seatbelt warning light onAuto Express warns that the Rover 75's seat SRS connector can cause the airbags to fail, and dealers were fixing it with revised connectors. The Dutch APK inspection puts the airbag or seatbelt fault warning among the most frequent defects across almost all series.
- Critical severityFrequency: OccasionalAlfa Romeo GiuliettaShort circuit from badly routed wiring that can prevent gear shifting (KBA campaign, 2010-2015)Yes: according to Germany's KBA, on Alfa Romeo Giulietta cars built between 2010 and 2015 inadequate cable routing could cause a short circuit and, as a result, gear-shift failure.
Frequently asked questions
Can I drive with code P0411?
Yes. According to the sources consulted, the car's driving barely changes with a warm engine, but the light will stay on and it will not pass an emissions test until you repair it.[1][2]
What is secondary air injection?
An electric pump that, only on a cold start, pushes fresh air into the exhaust to burn off unburnt fuel and warm up the catalytic converter sooner.[1]
Why does the code sometimes disappear?
Because the check is only carried out in a short window after a start with a completely cold engine, so the fault may not recur on other starts.[1]
Does the pump always need replacing?
No. It could be a stuck valve, a blocked passage, a relay or a fuse. One source suggests it is often a mechanical rather than an electrical fault.[1][2]
Will I pass the MOT with code P0411?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[3]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- P0411 – AutoDTCsAutoDTCs · Technical documentation · consulted 29 October 2026
- P0411: OBD2 diagnostic trouble codeCarista · Technical documentation · consulted 29 October 2026
- Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish