The Brake switch test provides information on which braking requirements are active via the hand and foot brake switch. If retarder operation is not possible, the reasons preventing it are displayed.
The Brake switch test is accessed via the Service group in the main window. Then select the Brake switch button in the Service menu.

The Brake switch test is offered depending on the connected ECU. The Brake switch test is not available without communication.
The display changes automatically after you have started the communication.