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The secondary air system supplies fresh air to the exhaust stream to reduce emissions through oxidation. Many systems also help bring the catalytic converter up to operating temperature quickly when the engine is first started.  

When the amount of air entering the exhaust is not what the powertrain control module (PCM) expects, the latter triggers the Check Engine Light to warn the driver about a possible P0411 code.

What Does the P0411 Code Mean?

Diagnostic trouble code (DTC) P0411 stands for “Secondary Air Injection Incorrect Flow Detected.” This code warns about a potential airflow issue in the secondary air system.

Note: Code P0411 is a generic code specified by the Society of Automotive Engineers (SAE). Depending on the car manufacturer, the code’s definition may change.

As was mentioned, the secondary air injection system reduces emissions by introducing fresh air into the exhaust system. Older vehicles have a belt-driven air pump while newer models have an electric pump.

closeup of exhaust system of a modern car
Code P0411 may get registered when the amount of air entering the exhaust is not what the powertrain control module (PCM) expects.

A traditional air injection system contains the following components: 

  • An air pump 
  • Pipes and hoses that transport the air from the pump to the exhaust manifold and/or catalytic converter 
  • A check valve in the air supply line that stops exhaust gases from flowing to the pump and other components 
  • Air management  that regulates the air supply

Depending on the operating conditions (and the system design), the air management valves will direct airflow to either the exhaust manifold, catalytic converter, or air cleaner. Typically, the valves are controlled by solenoids that are operated by the PCM. 

Nearly all modern secondary air injection systems use an electric pump rather than a belt-driven pump. Often, this setup is only used when the engine is cold to reduce emissions and bring the catalytic converter up to operating temperature quickly. 

The PCM monitors the secondary air injection system for faults. If it detects a problem, it turns on the check engine light and triggers a P0411 code. 

It’s worth noting that not all vehicles have a secondary air injection system. 

Users have reported P0411 for the following makes: Volkswagen (especially on a VW Jetta), Chevrolet, BMW, GMC, and Audi.

What are the Possible Causes of the P0411 Code?

  • Defective check valve and/or cutoff valve 
  • Bad or failing air pump 
  • Bad air pump relay
  • Failed air management valve  
  • Leaking system hoses or pipes 
  • Circuit issues, such as damaged wires or loose connections 
  • Accumulated carbon residue clogged or constricting the system
  • An issue with the PCM (e.g., software in need of an update) 
The secondary air injection system reduces emissions by introducing fresh air into the exhaust system
The secondary air injection system reduces emissions by introducing fresh air into the exhaust system.

What are the Common Symptoms of the P0411 Code?

Any malfunction in the secondary air system that prompts a P0411 code will ultimately affect the engine’s performance. 

Known symptoms may include:

  • Check Engine Light
  • Engine performance problems (e.g., rough running and lack of acceleration) 
  • Backfiring 
  • A rich running condition leading to poor fuel economy and potentially a rotten egg smell 

In most cases, a vehicle won’t show any signs of engine trouble despite logging a P0411 code. However, even if it doesn’t show these symptoms, bring it to a trusted auto repair shop once your scanner shows the diagnostic trouble code.

How to Diagnose the P0411 Code

Diagnosing the P0411 code can prove to be challenging, so you may want to just leave the job to your mechanic. But if you feel that your DIY car repair skills are sufficient, you can do the job yourself and figure out why the trouble code was triggered in the first place.

To help you diagnose the P0411 code accurately, check out the following video:

How to Fix the P0411 Code

There’s no single solution that could fix the P0411 code, just like pretty much all other OBD-II codes. This is why most people would just opt to leave the job to an automotive professional. 

But if you have the necessary automotive DIY skills, you can probably tackle the job yourself⁠—as long as you diagnose the underlying issue properly, of course. 

There are several avenues of repair for a P0411, such as cleaning the secondary air passages—a common fix on GMC Terrain vehicles. Make sure to figure out the appropriate resolution by researching some of the fixes other people have employed to address a P0411 on their vehicle (assuming it’s the same vehicle as yours).

As with any DIY repair, we advise that you utilize all of the auto repair resources and guides available online to help you figure out the proper steps to fix the P0041 code. You can also get an ALLDATA single-vehicle subscription, which will be useful for this fix and for any other future repairs your vehicle may need.

Don’t forget to consult your owner’s manual before attempting to fix the P0411 code.

Other Notes About P0411

A code P0411 bears some resemblance to other diagnostic trouble codes that also cover the secondary air system. 

Examples include:

  • P0410 – a general warning of an issue with the secondary air system
  • P0412 – denotes a malfunction with the solenoid that controls switching valve “A”
  • P0413 – denotes an open circuit in the solenoid that controls switching valve “A”

Products Mentioned in this Guide

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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