A plug adapter connects to a solenoid valve already mounted in a motor vehicle. The plug adapter has a plug connector for receiving an electrical control signal from a control unit of the motor vehicle for operating the solenoid valve. The plug adapter includes a solenoid valve connector for detachable coupling of the plug adapter to the plug connector of the solenoid valve. The solenoid valve connector and the plug connector are matched to one another in terms of plug form and electrical signal transmission. An electronics component, such as a microcontroller, processes an electrical output signal for operating the solenoid valve when an electrical connection is established between the electronics component and the solenoid valve via the solenoid valve connector when the plug adapter is plugged into the plug connector.