Cause
Loose or missing airbox lid
The airbox lid loose or absent, so air enters unfiltered and unmeasured. It is both faults at once — dust reaches the airflow sensor's element and the bore, and air bypasses the measurement.
The complaint is often a noise before it is a warning light: an intake roar or whistle under acceleration that the owner mentions first. Fuel trims run positive and the idle hunts. Check every clip is engaged and the lid sits flush — a lid clipped at one end and proud at the other is the classic, and it is nearly always a service that was rushed. A missing lid is also a fire and water risk in an engine bay, so it is worth more than a note on an invoice.
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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