There is no reset switch for the check engine light on your BMW 740ilL. The check engine light came on because the engine computer determined a fault with the engine control system. Please see the repairpal encyclopedia for more information about your check engine light. The check engine light can be turned off using a scan tool which can communicate with the engine control module. The light will also go off by itself after the repair has been made and certain conditions have been meet. The conditions vary depending on which fault code has been set.