What could be causing a Bosch dishwasher to not heat the water?
In most dishwashers, there's really only 2 or 3 parts that can cause this problem.

First is the heating coil itself. Disconnect it from whatever it's wired to. Measure the resistance of the coil with a multimeter. If it reads infinite OR 0, then the coil is bad. Anything in between and it's probably fine.

Next is the relay or the control board. On many dishwashers, the relay is on the control board. If yours is combined, then just buy a new control board. If the relay is separate, buy a relay because they are cheap. And if that doesn't fix the problem then it's the control board.