It is provided an adjustment mechanism, comprising a closure flap for at least partially closing a closure opening on a vehicle, via which, when the closure flap is opened, a connection element for connecting a line and/or a port for topping up a liquid, in particular a fuel, is accessible, a drive for adjusting the closure flap by external force in response to an operator control event, and an electronic control unit which is coupled to the drive and by means of which the drive is activated to open the closure flap in response to an operator control event which is detected in a contactless manner, and, on the other hand, is automatically stopped or reversed in so far as, when the closure flap closes, a possible obstacle is detected in a contactless manner in the adjustment path of the closure flap by means of an anti-pinch mechanism.