My cooling fan not coming on, I have checked all the fuses and swapped around relays but same problem.

If I short the relay contacts on the radiator fan low the fan spins

If I disconnect the wires to the temperature sensor the fan does not come on which I believe it should correct me if I am wrong.

If I remove the diode that seems to connect the ECM signal to the relay and use a test light probe to connect it to the negative battery terminal the fan comes on.

I am thinking that the ECM is not sending a signal to the relay to turn on the fan.

Can someone guide me as to what to look for going forward.
Thanks.