A method for operating a display device for a motor vehicle, having at least one first data acquisition means, having at least one second data acquisition means, having at least one first data outputting means which is connected to the first data acquisition means by a first data line and is connected to the second data acquisition means by a second data line, and having at least one first data processing unit, having the following steps: a. Detecting of at least one first datum by the first data acquisition means and converting of the first datum by the first data acquisition means into a first signal and detecting of a second datum by the second data acquisition means and converting of the second datum by the second data acquisition means into a second signal; b. Transmitting of the first signal from the first data acquisition means to the first data outputting means; c. Detecting by the first data processing unit whether the first signal is sent by the first data acquisition means and/or is received and/or output by the first data outputting means; d. Outputting of the first signal by the first data outputting means, if the first signal is sent by the first data acquisition means and is received and output by the first data outputting means, otherwise: e. Forwarding of the second signal of the second data acquisition means to the first data outputting means and outputting of the second signal by the first data outputting means; f. Transmitting of the first signal from the first data acquisition means to the first data outputting means and transmitting of the second signal from the second data acquisition means to a second data outputting means; g. Detecting by the first data processing unit and/or by a second data processing unit whether the first signal of the first data acquisition means is received and/or output by the first data outputting means and/or whether the second signal of the second data acquisition means is received and/or output by the second data outputting means; and h. Outputting of the first signal and of the second signal by the first data outputting means of the display device, if neither the first signal nor the second signal can be received and/or output by the second data outputting means, or Outputting of the first signal and of the second signal by the second data outputting means of the display device, if neither the first signal nor the second signal can be received and/or output by the first data outputting means, wherein, if one of the data outputting means (10, 18) fails, a split image is displayed on an existing screen, and wherein, if the first data acquisition means replaces a first exterior rear-view mirror and the second data acquisition means replaces a second exterior rear-view mirror, the views of which are each displayed in the first data outputting means and/or the second data outputting means, both displays are output by a screen. a. Detecting of at least one first datum by the first data acquisition means and converting of the first datum by the first data acquisition means into a first signal and detecting of a second datum by the second data acquisition means and converting of the second datum by the second data acquisition means into a second signal; b. Transmitting of the first signal from the first data acquisition means to the first data outputting means; c. Detecting by the first data processing unit whether the first signal is sent by the first data acquisition means and/or is received and/or output by the first data outputting means; d. Outputting of the first signal by the first data outputting means, if the first signal is sent by the first data acquisition means and is received and output by the first data outputting means, otherwise: e. Forwarding of the second signal of the second data acquisition means to the first data outputting means and outputting of the second signal by the first data outputting means; f. Transmitting of the first signal from the first data acquisition means to the first data outputting means and transmitting of the second signal from the second data acquisition means to a second data outputting means; g. Detecting by the first data processing unit and/or by a second data processing unit whether the first signal of the first data acquisition means is received and/or output by the first data outputting means and/or whether the second signal of the second data acquisition means is received and/or output by the second data outputting means; and h. Outputting of the first signal and of the second signal by the first data outputting means of the display device, if neither the first signal nor the second signal can be received and/or output by the second data outputting means, or Outputting of the first signal and of the second signal by the second data outputting means of the display device, if neither the first signal nor the second signal can be received and/or output by the first data outputting means,