P0411 Secondary air injection flow not as expected

Secondary Air Injection System Incorrect Flow Detected

Monitor

References and a dealer quoted in an NHTSA complaint describe a check engine light and emissions failure with no drivability change, but repair it so the car can pass inspection.

It gets more serious if:

  • Inspect soon: Get it checked soon if the air pump keeps running long after the engine has warmed up. A pump that never switches off can overheat.
  • Stop: Stop and switch the engine off if you see smoke or smell burning from the air pump area.

Source: how we rate severity

P0411 in short

P0411 means the engine computer ran the secondary air system after a cold start but did not see the expected extra air in the exhaust. Usual causes are a switching valve that will not open, a failed or water-damaged air pump, or a leaking hose. It rarely affects driving, but the car will fail an emissions test.

For a short time after a cold start, some engines blow fresh air into the exhaust so the catalytic converter heats up faster. An electric air pump supplies the air and a switching valve, often vacuum-operated, lets it into the exhaust.

To check the system, the computer runs the pump, opens the valve and looks for the result. Many systems expect the upstream oxygen sensor to read leaner while air is flowing; others use an air pressure sensor. If the change does not show up, or is too small, the computer sets P0411.

Because the test only runs during warm-up, the code can be intermittent. Several makers have also released calibration updates for false P0411 codes, so a dealer check for updates is worthwhile before parts are replaced.

Most likely causes

  1. Switching valve or combination valve that will not open

    Common general cause
    Why it ranks here
    Rick's write-up calls a switching valve that does not open the most common cause of P0411, and Carista lists a stuck-closed control solenoid or failed vacuum switching valve. Carbon buildup can hold the valve shut.
    What would change this
    Rises if the valve coil is open or the valve does not move when powered directly. Falls if it opens cleanly and air flows.

  2. Failed or water-damaged air pump

    Common general cause
    Why it ranks here
    Rick's write-up and Carista both name a failed pump. A dealer quoted in an NHTSA complaint found a 2000 Mustang's air pump full of water and burned out with P0411.
    What would change this
    Rises if the pump is silent at a cold start, water drains from its hose or it draws abnormal current. Falls if it runs strongly in an active test.
    How to test the secondary air pump

  3. Cracked vacuum hose or failed air hose

    Supported by vehicle data
    Why it ranks here
    Audi tied P0411 on 2000–2002 A6 and A8 to a cracked or broken vacuum hose, Cadillac tied it on the 1997–2001 Catera to a failed air hose, and a Volkswagen dealer quoted in an NHTSA complaint repaired a vacuum hose leak.
    What would change this
    Rises if a hose is cracked, collapsed or off its fitting. Falls if the hoses hold vacuum and air.
    How to test the vacuum hoses and intake leaks

  4. Engine computer calibration that sets a false P0411

    Supported by vehicle data
    Why it ranks here
    Ford (2000 Taurus) and Jaguar (2010 XF 4.2L) bulletins describe calibrations that can set P0411 without a real fault.
    What would change this
    Rises if a dealer finds a newer calibration for the vehicle. Falls if the computer is up to date and a component test fails.
    How to test the engine control module (ecm / pcm)

  5. Pump relay, fuse, check valve or wiring

    Possible — needs testing
    Why it ranks here
    Rick's write-up lists the pump relay, fuse, check valve and wiring. The Mustang dealer also replaced the relay with the pump. No bulletin names these alone.
    What would change this
    Rises if the pump gets no power at a cold start or a fuse is blown. Falls if power and ground reach the pump.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all codes, then ask a dealer to check the VIN for engine computer updates and secondary air bulletins.

    Low riskTool: OBD-II scan tool; VIN lookup at a dealer

  2. On a cold engine, start it and listen for the air pump for the first minute; then, engine off, look over the air and vacuum hoses.

    Low riskTool: ears; visual inspection

  3. Check the air pump fuse, then have power and ground at the pump measured during a cold start.

    Use cautionTool: multimeter

    Warning:Keep hands clear of belts and the fan with the engine running, and do not touch the pump or pipes: they get hot.

  4. Check the switching valve coil resistance, power it directly to see that it opens and closes, and look for carbon in it.

    Use cautionTool: multimeter, fused jumper leads

    Warning:Work on a cool engine and use a fused jumper; shorting the wrong pin can damage wiring.

Symptoms

  • Check engine light on with no change in how the engine runs
  • Fails an emissions or readiness check
  • No air pump sound right after a cold start
  • Air pump keeps running after the engine has warmed up Gets more serious: stop and have it checked.
  • Smoke or burning smell from the air pump area Gets more serious: stop and have it checked.

How to fix

  1. Ask a dealer whether an engine computer update applies to your VIN before replacing parts.

  2. With the engine off and cool, check the air and vacuum hoses around the air pump and switching valve and reconnect or replace any that are cracked or loose.

Parts and cost context

  • Secondary air pump:If water is found in the pump, find out how it got in before fitting a new one. Labor varies with pump location; get a quote.
  • Vacuum hoses and intake leaks:Cracked vacuum hoses to the switching valve are a known cause on some Audi models and cheap to rule out.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Audi

  • 2000–2002

    Supported by vehicle data

    A6 and A8: a cracked or broken vacuum hose can set P0411 with misfire and other air system codes. Bulletin status not verified.

  • 260702Status unverified

    MIL with P0300, P0411, P1128, P1130, P1411, P1423

    2000–2002a6, a8 · issued · NHTSA 10022452

    May be caused by a cracked or broken vacuum hose.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Ford

  • 2000 · Taurus

    Supported by vehicle data

    A PCM calibration can set a false P0411; flex-fuel models also have a bulletin for intermittent P0411. Bulletin status not verified.

  • 00T09Status unverified

    PCM calibration may set P0411

    2000taurus · issued · NHTSA 618538

    A PCM calibration strategy can turn on the MIL with P0411 when there is no fault.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Volkswagen

  • 1998–2001 · Jetta

    Supported by vehicle data

    Also Golf and New Beetle: Volkswagen issued several bulletins for P0411; a dealer quoted in an NHTSA complaint found a vacuum hose leak on a 2000 Jetta. Bulletin status not verified.

  • 0008Status unverified

    MIL on with P0411

    1999–2000golf, jetta · issued · NHTSA 616808

    MIL with P0411, secondary air incorrect flow; the flat-file summary gives no cause.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 0205Status unverified

    MIL on with P0410, P0411 or P1423

    1998–2001golf, jetta, beetle · issued · NHTSA 10000542

    Secondary air codes on Golf, Jetta and New Beetle; the flat-file summary gives no cause.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2008 · Colorado

    Supported by vehicle data

    Also Trailblazer, GMC Canyon and Envoy, Hummer H3 and Saab 9-7X: GM preliminary information for an intermittent light from P013B and/or P0411. Bulletin status not verified.

  • PIP-4361BStatus unverified

    Intermittent SES light from P013B and/or P0411

    2008canyon, envoy · issued · NHTSA 10026649

    Also lists 2008 Colorado, Trailblazer, H3 and Saab 9-7X; the flat-file summary gives no cause.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P2441Secondary air switching valve stuck closed (bank 1)

    Same system Possible — needs testing

    Systems that check each bank with a pressure sensor set P2441 for a bank 1 valve that will not open; P0411 is the broader incorrect-flow code.

  • P0418Secondary air pump relay A circuit fault

    Shares causes Possible — needs testing

    P0418 points at the air pump relay circuit. A pump that never runs because of its relay also leaves no air flow, so check P0418 first if both are stored.

All Secondary air injection codes

P0411 questions

Is it safe to drive with P0411?

Usually, yes. It mainly affects emissions in the first minute or two after a cold start. Stop if you see smoke or smell burning from the air pump area.

Why does P0411 come back after it is cleared?

The computer only tests the system during warm-up after a cold start, so the code returns on the next cold start if the fault is still there.

Sources and review

  1. P0411 OBD-II diagnostic trouble code — Carista
  2. NHTSA complaint ODI 764058: 2000 Ford Mustang, P0411 with water in the air pump — NHTSA Office of Defects Investigation (complaint flat file) ,
  3. Recall 16V-738 (Subaru WTM-73): secondary air injection pump relay — Subaru of America / NHTSA (read via vehiclesafetyrecalls.com and recallcheck.net) ,
  4. Secondary air injection system incorrect flow detected (P0411) — Rick's Free Auto Repair Advice (Rick Muscoplat) ,
  5. MIL on with P0300, P0411, P1128, P1130, P1411, P1423: cracked or broken vacuum hose (Audi bulletin 260702) — Audi of America / NHTSA ,
  6. P0411 from a failed air hose (Cadillac bulletin 181200) — General Motors (Cadillac) / NHTSA ,
  7. NHTSA complaint ODI 767153: 2000 Volkswagen Jetta, P0411 vacuum hose leak — NHTSA Office of Defects Investigation (complaint flat file) ,
  8. PCM calibration may falsely set P0411 (Ford bulletin 00T09) — Ford Motor Company / NHTSA ,
  9. Engine MIL with P0411: false secondary air detection (Jaguar bulletin TB-K050) — Jaguar Cars / NHTSA ,
  10. Understanding Tacoma P2441 and P2445 codes — Rick's Free Auto Repair Advice (Rick Muscoplat) ,
  11. P0418 code: secondary air injection system relay A circuit — Kelley Blue Book (KBB Service Advisor, reviewed by Gary Hardesty)
  12. MIL on with P0411 secondary air system incorrect flow detected (Volkswagen bulletins 0006 and 0008) — Volkswagen of America / NHTSA ,
  13. MIL on with P0410, P0411 or P1423 (Volkswagen bulletins 0204 and 0205) — Volkswagen of America / NHTSA ,
  14. Intermittent SES light from P013B and/or P0411 (GM PIP-4361B) — General Motors / NHTSA ,
  15. Final Regulation Order: 13 CCR §1968.2, Malfunction and Diagnostic System Requirements (OBD II), 2004 and subsequent model-year passenger cars, light-duty trucks and medium-duty vehicles (2015 amendments) — California Air Resources Board
Last reviewed
Written by
Saurabh K.
Editorial review
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