If the fan is working sometimes then we can assume (for now) it is not the fan itself. However, we need to check the voltage at the fan on the white/black wire from the PCM, because you have a micro processor as part of the motor.
Also, I just want to confirm you have the single fan set up and not dual fans?
If you have dual fans then this is a different issue. However, I suspect you have a single fan, so if you do not have voltage at the motor when the fan should be on, then we need to make sure the cylinder head temp sensor is working. If the engine is actually overheating or the gauge is showing that it is overheating then the fan should be coming on.
At that point, the PCM is the likely issue as it should be commanding it on and it is not.
Below is the wiring diagram that will show where we need to test this voltage.
Please run through this and let me know what questions you have.
Wednesday, September 8th, 2021 AT 7:51 PM