This indicates a heater failure, and once it occurs, the unit is locked up. You need to verify the element is connected electrically to the control board and that it isn't an open circuit. Also, make sure the door catch mounted to the top of the tub is bent down enough to just clear the inner door panel to ensure the heater return switch is closing properly. Finally, the board must be reset once an error has occurred. Press the HEATER DRY, NORMAL, HEATED DRY, NORMAL keys in sequence. All the display lights should turn on, then press cancel and give it a try. If the control board doesn't see an expected temperature rise when the heater is turned on, it figures the heater has failed and displays this error. So you much check the entire heater circuit to ensure it works. And make sure water is actually pumping because without water spraying around in the tub, the water will never contact the heater and thus, never heat up. Finally, run your water hot at the tap before starting the dishwasher.

Glad I could help.