The main function of the thermostat heater is to constantly control the flow or passage of coolant. It also regulates the operating temperature of the engine. To perform these functions, the thermostat is supplied with 12 volts from the ECM (Engine Control Module), which is the power supply.
A malfunction of the engine thermostat results in the setting of various fault codes, which warn the driver of such a condition. Specifically, the P0599 OBD2 fault code is a generic code, which shows that the ECM found a high circuit in the thermostat heater.