Cooling Fan Circuit [11/2016 - ]: Description
WARNING: This page is about a different car, the 2019 Toyota Highlander, 2018 Toyota Highlander, and 2017 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
The ECM calculates an appropriate cooling fan speed based on the engine coolant temperature, air conditioning switch condition, refrigerant pressure, engine speed and vehicle speed. The cooling fan ECUs control each cooling fan speed based on the duty cycle calculated by the ECM. By optimally controlling the cooling fan speed via the cooling fan ECUs based on the conditions of the vehicle, the ECM can achieve both high cooling performance and quietness.