P2440: Secondary Air Injection System Switching Valve Stuck Open Bank 1
What to do
Expect poor fuel economy, possibly a smell of unburnt fuel, and a rough idle. If lean codes or lean fuel trims have been reported alongside this, do not let a vacuum leak hunt be the plan — a secondary air valve stuck open pumps air into the exhaust, which makes the oxygen sensors read lean when the mixture is fine, and the module then adds fuel until the engine genuinely runs rich. Fixing the valve resolves the lean readings. Worth doing promptly, since sustained over-fuelling is what destroys catalytic converters.
What this code means
The switching valve on bank 1 is not closing when the secondary air system shuts down. This is the fault in the whole family that causes a driveability problem, and it does so by a route nobody expects — so it gets diagnosed as something else entirely.
The system is only safe when it runs at the right moment. Secondary air injection exists to add oxygen to the exhaust for the first thirty to ninety seconds after a cold start, while the catalyst warms. After that it must stop completely, and the switching valve is what seals the path.
Air entering the exhaust at any other time breaks the mixture measurement. The upstream oxygen sensors measure oxygen. They cannot distinguish oxygen that survived combustion because the mixture was lean from oxygen that was pumped in downstream of the cylinders. So a valve stuck open feeds air past those sensors continuously, and they report a lean mixture that does not exist.
What the module does next is the expensive part. Believing the engine is running lean, it adds fuel. The sensors still read lean, because the extra oxygen is still arriving, so it adds more, and the fuel trims run to their positive limits and stay there. The engine ends up running genuinely rich because a valve failed to close — with the fuel consumption, the fuel smell and the catalyst overheating that go with it.
That is the same shape as the stuck sensor argument at P2195, reached from a different direction, and it produces the same misdiagnosis: lean codes and lean fuel trims on an engine with no lean condition. Vacuum leak hunts on a car with a stuck-open secondary air valve find nothing, because the unmetered air is entering the exhaust rather than the intake.
The usual physical cause is not the valve's electrics. It is carbon at the exhaust junction and corrosion from the exhaust moisture the check valve was meant to keep out — the same environment that destroys the pump, described at P2257.
Likely causes
Start here
- Carbon deposits holding the valve open · moderate
- Faulty secondary air switching valve · moderate
- Failed secondary air check valve · moderate
Less common
Symptoms
Components involved
Information, not instruction
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Community experience
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