Cause
Condensation in the fuel tank
Water condensing inside the tank from humid air drawn in as fuel is used. Every tank breathes, and warm damp air entering a cool tank leaves water behind — which then sits under the fuel because it is denser.
It is worse in vehicles used little and kept part-full, since a large air space cycles more air through more temperature swings. The symptoms are erratic and follow fuel level: misfires and pressure faults as the pickup draws slugs of water, worse as the tank empties. Keeping the tank fuller reduces it, which is a genuine piece of advice rather than folklore. On a diesel it reaches the water trap, which is what the trap is for; on petrol it can freeze in the lines in winter, which is the version that strands people.
Typically an easy fix. Often worth checking before paying anyone to look.
Some of these codes mean you should stop driving
1 of the 1 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (1)
Codes where this is a likely explanation first, rather than merely a possible one.
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