When you say "codes don't clear" are you saying they don't go away or you can't clear them with the scanner? AFAIK the Valvetronic calibrates itself everytime you turn the key but I'm only starting to tinker with mine a bit (N52) getting to know how it works.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)