This happens if no thermistors are connected or the thermistors have a short or are broken or are plugged on the wrong pins or configured wrong. Or the motherboard has a fault.
Unfortunately this firmware sets defective on both thermistors and doesn't tell you which one is causing the issue.
Unplug the thermistors from the board. Measure the thermistor resistance including the full cable length from the thermitor cable plug. Should be about 100k at room temperature.
If they read OK, the firmware is reading the wrong pins, or a damaged pins on the controller.
Edited 1 time(s). Last edit at 02/01/2020 12:03AM by Dust.