How are you checking the water temp? In order to accurately check the warm rinse temperature, you must check the temperature of the water in the tub after it is filled. Should be around 85°. You can't just feel the temperature of the water coming in because in warm setting, the hot water valve is on all the time while the cold valve is cycled on and off by the auto temp control portion of the control board to get the final full tub temperature correct. If the full tub temperature is too high, you may have a faulty thermistor which would require replacing the entire water valve assembly. I would first check the inlet screens for debris and make sure you have good water flow through each water hose.

Eric