P0411: Secondary Air Injection System Incorrect Flow Detected

What does the P0411 error code mean?

The diagnostic trouble code, or DTC, P0411 stands for "Secondary Air Injection System Incorrect Flow Detected." The code occurs when your vehicle's engine control module detects that the airflow from the secondary air-injection system is not within specifications. It's worth noting that this issue will only be present on cars equipped with secondary air-injection systems, such as vehicles originally sold in California. Secondary air-injection systems pump fresh air into the exhaust stream to help reduce emissions during cold engine startup.

Why is this issue important?

The secondary air-injection system plays a key role in reducing hydrocarbon emissions by ensuring more complete combustion during engine warm-up. If the system is not functioning properly, the vehicle may emit more pollutants, fail emissions tests and experience reduced fuel efficiency.

Your car's secondary air-injection system is critical in helping reduce tailpipe emissions when you cold-start your vehicle. As the name implies, a cold start occurs when the engine is totally cold, such as after being left to sit overnight. This period can produce particularly high tailpipe emissions, and a secondary air-injection system failure will result in the emission of more pollutants, failing emissions tests and more.

Can I safely drive my car with this error code?

You can drive with a faulty secondary air-injection system, but the system's faults will lead to performance issues. More serious ones, like rough running or worse fuel economy, usually only occur in severe cases, and you certainly won't be passing an emissions test. You may also see reduced fuel economy as a result of the system's failure.

Common symptoms of the P0411 error code

• Illuminated check engine light 
• Failed emissions test
• Increase in exhaust smell during startup; drivers often compare the scent to rotten eggs
• Possible hesitation or rough idle during cold starts (rare)
• Poor fuel economy
• Backfiring

How is the P0411 error code diagnosed?

• Scan tool confirmation: Verify the code using an OBD-II scanner.
• Visual inspection: Check for damaged or disconnected vacuum lines, air hoses and wiring.
• Air pump operation test: Ensure the air pump activates at startup.
• Check valves and solenoids: Test for proper function and air flow.
• Exhaust backpressure test: Assess if air can enter the exhaust system correctly.
• Engine control module and sensor review: Evaluate related sensors and control signals.

How is the P0411 error code repaired?

• Replace or repair faulty secondary air injection pump.
• Repair or replace damaged vacuum or air hoses.
• Replace failed air injection solenoids.

Related reading

Follow the link below to reach our catalog of diagnostic check engine trouble codes:
On-board diagnostics (OBD-II) trouble code directory