Just look under "engine wiring harness" but are sure you really need that?? it's going to be pricey, maybe a used one ?? It's 12517531986 for after 10/03 (I looked for mine but will give you an idea) over $600 on FCP!

I can see your point though, if a lot of people have been working on the vehicle and you have maybe broken connector housings and maybe suspect ruined/expanded contacts which can be intermittent and really hard to pin down. This would be in addition to changing the sensors (especially the crank) to OE, not instead right?

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