Secondary Air Injection System Stuck Off (Bank 1)
The secondary air injection system isn't working properly on bank 1.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The secondary air system is supposed to inject fresh air into the exhaust to help reduce emissions, but it's not doing that right now.
What the computer is actually seeing
The engine control module (ECM) expects to see a certain amount of pressure in the secondary air injection system shortly after startup and during low engine loads, usually when the engine is still warming up. If it doesn't see the expected flow or pressure, it triggers the code.
What a healthy reading looks like
Pressure readings from the secondary air injection system should be around 5-10 inches of water column during operation. If the system is active, the air pump should run for 15-20 seconds after the engine starts.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the wiring and connectors to the secondary air pump for damage or corrosion. If found, repair or replace as needed. Decision: If wiring is intact, proceed to Next Step.
- 22. Check the secondary air pump operation by applying direct battery power to the pump. If it runs, it's good. If not, replace the pump. Decision: If the pump is working, proceed to Next Step.
- 33. Inspect the air injection passage for blockages or restrictions. Clean or repair anyidentified issues. Decision: If passages are clear, proceed to Next Step.
- 44. Test the pressure sensor in the secondary air system. Use a multimeter to check for proper output voltage (typically around 1-5 volts). If out of range, replace the sensor. Decision: If the sensor is functional, consider further diagnosis for ECM issues.
Common causes
- Faulty secondary air pump
- Clogged or damaged air injection passage
- Faulty pressure sensor
- Wiring or connector issues
- Check valve failure
Typical repair cost
$$$
Related codes
Frequently asked questions
Can I still drive the car with this code?
Yes, but emissions may be higher than normal and it could fail an emissions test.
Will this code come back after I clear it?
If the underlying issue isn't fixed, the code will typically return after a few drive cycles.
Why does this code appear with P0411?
P0411 indicates a flow issue in the secondary air system, which often occurs due to the same underlying failure that triggers P243B.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →