P0416 indicates the engine control module has detected an open electrical circuit in the secondary air injection switching valve B. This valve controls the routing of fresh air into the exhaust stream during cold starts to reduce emissions. An open circuit means the solenoid or wiring has a break that prevents electrical current from reaching the component.
The internal coil of the electric switching valve has burned out or broken internally, creating an open circuit that the PCM detects.
A break, chafing, or disconnect in the wires between the PCM and the valve prevents electrical continuity.
Moisture intrusion or oxidation at the valve's electrical connector creates high resistance or a complete open circuit.
The terminal pins at the engine control module connector may be damaged, corroded, or backed out, interrupting the circuit.
In rare cases, the output driver inside the engine control module that supplies power or ground to the valve has failed.
Generally yes. The engine will run normally, but emissions will be higher during cold starts and the vehicle will likely fail an emissions inspection.
Not immediately. The secondary air system helps the catalyst warm up faster; without it, the catalyst may experience slightly more thermal stress over time, but catastrophic damage is unlikely.
Almost never. This code almost always indicates a failed switching valve solenoid or wiring issue. Replace the PCM only after verifying the valve and all wiring are good.
It is an electrically operated solenoid that controls the flow of secondary air from the injection pump to the exhaust system, typically switching between different banks or between the exhaust manifold and catalyst.