All Bosch dishwashers (and most modern appliances that use electronic control boards) store fault codes pertaining to specific areas the appliance is having a problem with... or at least the areas that the control board thinks is having a problem. Anyway, it's a good place to start. These control boards all have a secret key dance to enter that secret service mode and receive those error codes.
Now, for the first time ever in the history of the Interwebs, Brother PDuff reveals the super secret key dance to enter service mode and retrieve the stored error codes. Let's listen in...
You can try to access the test program to retrieve possible fault codes:
With the door closed, press and hold the second and fourth buttons to the right of the display while pressing the On button.
As long as these two buttons are pressed, the associated leds will light, then the display will show the model coding identifier. Release the two buttons.
Press the same two buttons to display any stored fault codes:
0 = No fault
1 = Fault in Hydro Sensing system
2 = Heater fault
4 = Fill fault
8 = Fault in NTC system
16 = Water switch cannot be positioned
Note: If more than one fault is detected, the fault code is added up. Ex: Fault code 3 = fault 1 + fault 2.
Press Off to exit.
Source: Bosch Dishwasher heatin problem