P0410: Secondary Air Injection System A
What to do
Driveable, and usually with no symptom you would notice. It will fail an emissions test. If you have heard a loud whirring noise for a minute after a cold start and it has recently stopped, mention that — it is the pump, and its absence is a useful clue.
What this code means
The secondary air injection system is not behaving as the module expects. Its purpose is narrow and easily misunderstood: for the first minute or two after a cold start, a pump forces fresh air into the exhaust ports or upstream of the catalytic converter. The extra oxygen lets unburnt fuel in the cold, rich exhaust continue burning, which both reduces tailpipe emissions during the worst part of the cycle and heats the converter to operating temperature sooner.
Because it runs only briefly and only when cold, the system is invisible in normal use and its faults are almost never noticed by a driver — the code appears at an emissions test or during a routine scan. Testing it requires either a genuinely cold engine or a scan tool that can command the pump, and trying to diagnose it on a warm engine wastes an afternoon.
Likely causes
Start here
- Failed secondary air injection pump · moderate
- Carbon-blocked secondary air passage · moderate
- Seized secondary air check valve · moderate
Less common
- Faulty secondary air switching valve · moderate
- Faulty secondary air injection relay · easy
- Water damage to the air pump · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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