Cause
Intake duct disconnected or split
The intake duct off its stub or split open between the airflow sensor and the throttle. Everything it admits is air the engine never measured, so the mixture goes lean and the module's corrections chase a quantity that was never counted.
A duct that is fully off is obvious; a split is not, particularly on the underside of a bend where it closes when the engine is off. The fault often appears only under engine movement or load, which is what makes it read as a failing sensor. Flex the ducting by hand with the engine running — an idle that changes as it is squeezed locates it immediately. Suspect it after any work in the engine bay, since these are removed to reach almost everything.
Typically an easy fix. Often worth checking before paying anyone to look.
Codes this can cause (1)
Codes where this is a likely explanation first, rather than merely a possible one.
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