Diagnostic Test Code (DTC) P0411
is defined by SAE J2012 as "Secondary Air Injection System Incorrect Flow Detected"
This DTC runs when the air injection pump and the air injection control solenoid do not have any detectible electrical faults. The PCM commands the pump to run and the solenoid to open and add forced air to the exhaust stream. The PCM then looks at the oxygen sensors in the exhaust to see if there is added oxygen in the exhaust as expected. If the oxygen sensors do not indicate that added oxygen is present, DTCP0411 sets.
There is also an air pressure sensor involved in this system, but I have never replaced one of these...failure is rare.
With all that said, I have replaced MANY air injection control solenoids to fix this fault. I have also replaced a couple pump motors, but not nearly as many as the solenoids.
The air injection pump is located under the vehicle below the driver's seat. You should be able to hear it running occasionally - it sounds like a small vacuum cleaner when it runs. If the pump runs, this is not likely to be the problem and you will most likely have to replace the solenoid.
The solenoid is located on the right side of the cylinder head. (see diagram)