The float can get stuck. Either bent and hitting the side or on one of the hoses (happened to me). (Also non standard float shape on aftermarket).

More often it's the wiper loses pressure and you can restore proper function by disassemble and bend the wiper to have more pressure.

I made a thread on the subject search awr-fix in advanced search in title y did find it.

Also run test 21 after to reset the computer or it will take a couple tanks before it reads correctly.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)