Dishwasher is not drying glasses or getting hot enough on Sanitize or Pots cycles. Hot water heater is on 135 degrees. Could it be that the heating coil at the bottom of the washer is burned?
Here are your parts
Replacement parts for FRG PLDB999CC0 | AppliancePartsPros.com
Here is a wiring diagram / tech sheet
http://manuals.frigidaire.com/prodinfo_pdf/Kinston/154444501.pdf
Yes it could be the heating element.
Remove the wire from one side of it and measure it with a meter.
Should be around 15 ohms.
Could also be the thermostat.
Should be 0 ohms at room temperature.
Could be the control board.
Measure voltage P5 to W. One side of the HiLimit Thermostat to the far side of the Heating Element. Should be 120 volts when cycle is telling the unit to heat.