xps 8920 and H80i v2 cooler upgrade: cpu fan error because of missing pin

[Plastified]

After installing a Corsair h80i v2 cooler into an XPS 8920 special edition i7-7700k, I get a cpu fan error on boot up, despite the fans and pump working perfectly.
It looks like it is related to the fact that the 3-pin pump connector connects into a 4-pin CPU_FAN connector on the motherboard (the 4th unused pin is usually for the fan tachymeter wire). The pump does not have a tachymeter and the motherboard freaks out.

Facts:
-The XPS 8920 BIOS doesn't allow deactivation of the CPU_FAN check (i.e. missing signal from 4th wire).
-4 wires comes out of the two fans, which are hooked up in the water cooler.
-The water cooler pump has a 3-pin fan connector which connects into the CPU_FAN header of the motherboard as per the manual.

Is there an easy way to split the outgoing tachymeter signal from one of the two fans (which both have each 4-wire connectors) and send that single wire signal into the unused CPU_FAN header ?

Is there another easy way to circumvent this problem ?

Thank you so much for your help.