What does P0410 secondary air injection system mean?
Short answer: The engine computer did not see the expected oxygen sensor response when it commanded the secondary air pump during cold start, pointing to a failed pump, stuck valve, blocked passages or wiring problems.
Secondary air injection pumps fresh air into the exhaust during a cold start to heat the catalytic converter quickly. The computer tests the system by watching the upstream oxygen sensors for a lean signal when it turns the pump on.
Common failures include a pump that has seized or filled with water, a check valve that is stuck or leaking, carbon-blocked passages in the cylinder head or manifold, a failed relay or a blown fuse. Some vehicles have pressure sensors in the system that set more specific codes.
Command the pump on with a scan tool and listen for it. Check power and ground at the pump, and inspect hoses for melted or cracked sections, which suggests exhaust has backed up through a failed check valve. Test with a cold engine, since the system normally runs only after a cold start. Follow service procedures, as blocked head passages may require extensive cleaning.
Tools used for this job
General guidance only. Follow the vehicle and tool manufacturer's procedures, and confirm vehicle coverage on the tool maker's list before buying.