SFI SYSTEM


  1. OPERATION


    1. The cooling fan control system achieves an optimal fan speed in accordance with the engine coolant temperature, vehicle speed, engine speed, and air conditioning operating conditions. The ECM calculates the appropriate fan speed and sends signals to the cooling fan ECU. Upon receiving the signals from the ECM, the cooling fan ECU actuates the fan motors.

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    2. As illustrated below, the ECM determines the required cooling fan speed by selecting the fastest fan speed from among the following:


      1. The fan speed required according to the engine coolant temperature (Graph 1).

      2. The fan speed required based on the air conditioning refrigerant pressure (Graph 2).


        • When the air conditioning refrigerant pressure is within the lower part of the normal operating range with the air conditioning pressure sensor on, the required fan speed differs according to the vehicle speed.

        • When the air conditioning refrigerant pressure is higher than a specified upper limit, the required fan speed will increase based on an emergency request from the ECM.

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