Try a new relay first, i have had to replace brand new items as they have failed on first use.
Then it will be Time to get the multi meter out and do some wiring checks.
The ECU controls the fans, first you will need to check the wire from the temp sender to the ECU has good continuity, as well as the ECU to the fan relay has good continuity, ie. very low ohms with power removed. Also check the earths for these circuits.
You then need to find out if the ECU is telling the fans to come on. You should get 12v out of the ECU to engage the fan relay.
If you have good continuity on all the wires and you dont get the 12v signal from the ECu to the fan relay, the ECU is likely to be the cause of the fault.
As for pins on ECU or ralay to check, that you will have fugure out your self.