What does a BMW electronic thermostat control open circuit fault mean?

[SanWilliam]

BMW electronic thermostat control open circuit fault means that it is necessary to check whether the engine cooling system heater control circuit is open or whether the heater is damaged. How the electronic thermostat works: The ECU provides a duty cycle (PWM) signal operating voltage to the heating resistor element inside the electronic thermostat based on the calculated value derived from sensor signals, causing the wax to expand and displace. The temperature regulation unit mechanically adjusts the coolant flow between the large and small circuits through this displacement. How to handle an electronic thermostat control open circuit fault: Check whether the electronic thermostat connector is loose. If there is no loose connection, use a multimeter to measure the resistance of the electronic thermostat. If the resistance is infinite, it indicates an internal open circuit in the electronic thermostat, and the thermostat should be replaced.