This could be the ECT but we need to see what the ECM is seeing from the ECT sensor. The sensor could be fine but if the ECM is not reading properly then it will not turn it on. You should have two fans. One turns on based on the coolant temp and the other only turns on when the AC is on.
So we can test the sensor and if faulty then that may be the result but if it tests ok, then we need to monitor the ECM with a scan tool and see what it is reading.
Images (Click to enlarge)
Wednesday, December 4th, 2019 AT 3:32 PM