Yeah, there should have been a platic lock on the cover to prevent you from opening it. It that was already broken then someone (not a dealer) was looking in the dipstick hole and didn't replace the cap with a new one. The tool to measure the level is about $50 IIRC and you will need one if you want to change the fluid yourself. Like I said, the 722.6 is really not all that DIY friendly other than just simple fluid and filter changes and any faults are best read from stored codes by the SDS system at the dealership.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz