In case of a fault arising with the transmission, it is always important to find out if it is an electrical, mechanical or hydraulic fault and this needs testing equipments. For this reason, it should be performed by a BMW dealer or with a specialist with an appropriately equipped workshop if a transmission problem is suspected. Also, do not have the transmission pulled out of the car for possible repairs before having professional fault diagnosis done as most tests have to be run with the transmission in the car.