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2006 e90 330xi 6 speed. I recently went to the mechanic to get some serious work done (all four aluminum head bolts were broken). The mechanic came back after the repair and said the car has a check engine light for tank venting valve. This is a $100 part. I scan my car regularly and would have definitely provided it if I would have known the issue.

I asked the mechanic to confirm the wiring harness connections since some of the harnesses were disconnected/removed and check if it's a low voltage related issue due to old battery.

He came back and confirmed that the code was triggered by low voltage and doesn't show up anymore. Is this possible? I know some codes can show up from low voltage, but what about the actual fuel ventilation valve by the throttle body? Please help! Picking the car up shortly, don't want to get it back with an issue. Although, this piece is fairly accessible, but am worried that the harness or connector were damaged.

[Suvorovo]

Non issue. Never came back.