Communication system for motor vehicle

A communication system, a vehicle (100) with such a communication system (201) and a method, for transmitting a radio message, indicating an unauthorised access to the motor vehicle (100), from a radio transmitter in the communication system is described. A message for triggering the transmission of the radio message is sent from an electronic control unit (202) in the communication system (201) to the radio transmitter for only when power is received from a main power input (211).