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.
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.
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.
A traditional air injection system contains the following components:
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.
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.
Any malfunction in the secondary air system that prompts a P0411 code will ultimately affect the engine’s performance.
Known symptoms may include:
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.
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:
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.
A code P0411 bears some resemblance to other diagnostic trouble codes that also cover the secondary air system.
Examples include:
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