A method for monitoring a door contact switch of a driver's door of a motor vehicle locked in an idle state includes detecting an unlocking of the driver's door of the motor vehicle, and detecting whether a change in a door contact signal of the door contact switch takes place after the unlocking of the driver's door. If a change in the door contact signal has been detected, a plausibility counter is initialized, otherwise the method includes detecting whether a drive unit of the motor vehicle is activated. A “door contact implausible” state is established and the plausibility counter (P) is incremented if the activation of the drive unit has been detected in step d).