Heater was delivered too much power, causing the overtemperature switch to open. RTD is not reading properly. After the heater cools down, replace RTD. Switch closes and the error can be cleared when the heater temperature falls below 190°F(87°C).
If heater is not actually over temperature, chack all wiring and connections between the TCM and the overtemperature switches.
Replace overtemperature switch.