P0410: Secondary Air Injection System (AIR System A) Fault
P0410 means the engine computer found a problem with secondary air system A, the system that blows fresh air into the exhaust after a cold start to cut emissions. It is not urgent because driving is unaffected, but the check engine light stays on and the car can fail an emissions test.
You can keep driving
The data says driving is unaffected and limp mode is not expected. The only effects are a lit check engine light and higher emissions right after a cold start, so repair it soon but you do not need to stop driving.
What it means
After a cold start, an air pump (the AIR pump) pushes fresh air into the exhaust right behind the exhaust valves. This burns off unburnt fuel and helps the catalytic converter warm up faster. A shut-off valve opens the air path and stops exhaust from flowing back into the pump. P0410 is the general function code for this system. On many Bosch-managed engines the computer checks it by running the pump and watching the front oxygen sensor, which should read lean (extra oxygen) or make the fuel control react. If no air is detected, the code is set. Some makes use the code differently, and Saab's Motronic 900 uses it for too much air. The check runs once per trip after a cold start, so the light may not return until the next cold start.
Likely causes
- Secondary air pump failed (water ingress, seized)Very likely
If the pump does not run or is seized, no air reaches the exhaust and the oxygen sensor sees no lean signal.
- Combination or shut-off valve carboned up or stuckVery likely
Carbon buildup can keep the valve from opening, so the pump's air never gets into the exhaust.
- Vacuum hose or electric changeover valve leaking or faultyPossible
The valve is opened by vacuum, so a leaking hose or a faulty changeover valve keeps it shut.
- Pump relay or fuse faultyPossible
Without power from the relay or fuse the pump stays silent after a cold start.
- Air ducts in the head carboned up or hose offPossible
Blocked passages or a disconnected hose stop the air from reaching the exhaust ports.
What you may notice
- Check engine light on
- Secondary air readiness not set (emission test)
- Pump silent after a cold start, or unusually loud
- Driving normal, higher cold-start emissions
What to check, cheapest first
- 1Start the engine cold and listen for the air pump running for a short time. Silence or an unusually loud noise points to the pump. · you can do it
- 2Check the pump fuse and relay, and swap the relay with an identical one if possible. · you can do it
- 3Inspect the air hoses and vacuum hoses for cracks, leaks or a hose that has come off. · you can do it
- 4Read the stored code and any related codes (such as P0411, P0412 or P2440) to see which part of the system is involved. · mechanic
- 5Test the pump and the electric changeover valve by commanding them with a scan tool and check that vacuum reaches the shut-off valve. · mechanic
- 6Inspect the combination valve and the air ducts in the head for carbon buildup, then clear the code and complete a drive cycle (a cold start and trip) to confirm the repair. · mechanic
Related codes
Frequently asked questions
Can I drive with a P0410 code?+
Yes. Driving is unaffected. Cold-start emissions are higher and the check engine light stays on, so have it repaired soon.
Can a loose gas cap cause P0410?+
No. The code is about the secondary air system, not the fuel system. The usual causes are the air pump, the valves, hoses, or the relay and fuse.
Will P0410 pass an emissions test?+
Probably not. The check engine light is on and the secondary air readiness monitor will not be set. Repair it and complete a drive cycle first.
Can I fix P0410 myself?+
Sometimes. The repair is rated medium difficulty and DIY is possible, with an estimated 0.5 to 3 hours. Checking the fuse, relay and hoses is a good first step.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10