GE Dishwasher Error Codes (PDT760SSF4SS)
Searching for GE Dishwasher Error Codes (as they generally aren't model-specific), I found the following page: http://www.searspartsdirect.com/dishwasher-repair/error-codes/ge-dishwasher-error-codes.html

F51 is "Temperature sensor failure"; "Shut off power to the dishwasher and check the wiring connections on the temperature sensor, which is located on the flood switch. Check the resistance of the temperature sensor. It should measure about 11,000 ohms at room temperature. Replace the flood switch if the temperature sensor is defective."

F65 is "No water detected by the inverter control board": "If the dishwasher didn't fill, make sure that your water supply cut-off valve is open. Replace the water inlet valve if defective. If the dishwasher did fill, shut off power to the dishwasher and check inverter control board wiring. Reconnect any loose wires. Replace the wire harness if damaged. If the wiring is okay, replace the inverter control board."