3.0i M54 engine keeps tripping the Service Engine Soon light.
Peake engine code tool reports two errors. They're both basically the same, just different cylinders:

F5: Secondary air system flow too low, cyl 1-3
F6: Secondary air system flow too low, cyl 4-6

If I reset it, its gone for a few day, then SES light back on.

Do you know what this could mean / which part might be failing, or which electrical connection to check? Or, keeping in mind, I guess it could just be a sensor that is going out and reporting falsely.

Thanks so much.