I don't recall discussing a sensor covered in oil as a cause, more likely oil on a breather, but I could be wrong. I did agree, above, that the steering leak and its repair could be related to the CEL. The most likely connection, in my mind, would be due to something in the evaporative emission control system being disturbed when the steering hose was being changed. I expect electrical connections are sufficiently sealed.

Striving for correct information without the acerbic comments...

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue