Cause
Blocked evaporative system filter
The filter on the evaporative system's fresh air inlet, blocked so the system cannot draw air. The vent is open to atmosphere by design, and this filter is what stops dust and water entering the canister — which is exactly why it clogs.
A blocked filter behaves as a blocked vent. The tank cannot equalise, so it draws into vacuum as fuel is used, fuel delivery suffers as the tank empties, and there is an audible rush when the filler cap is opened. The leak monitor also cannot run, because the system has no air to draw.
Its position is what fouls it — usually under the vehicle near the canister, where road spray, mud and salt reach it. Check it whenever the vent path is suspected, since it is cheap and frequently overlooked in favour of the vent valve. Insects and spiders nesting in the inlet are a genuine and surprisingly common blockage in the same location.
Typically an easy fix. Often worth checking before paying anyone to look.
Codes this can cause (2)
Codes where this is a likely explanation first, rather than merely a possible one.
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