If windshield is not OEM sensor is fail or sometime , like it was in my situation , did not work at all. After installation of original BMW glass rain sensor workin just fine till present time ( about 2 years since ).
Now if your winshield is original , first try to take ( borrow from other guy ,who has the same model x5) a new sensor ( 200 usd usually) replacement is fearly easy and you can do it yourself. Be caryfull with plastick hooks on windshield ,when reattach sensor itself, by not braking them .
If that does not help ,-you need to replace a stearing wheel column regulator. Step by step. Good Luck
please revieu when you'll finish succesfully