I have the same problem.
I have tried doing that to no sucess...
There is definitely one maun header of the two coming from the pump, i noticed because unplugin the non-main one made me have rpm response on screen (in-app), but unplugin the main one cuts rpm response to zero on screen.
Still it resorted in failure... rpm is 1320-1400 constantly.
I noticed that the main pwm header coming from the pump has 4 pins and the non-main one as 3 pins, but the 3rd one is at the left far side. And my fans have only 3 conectors. Could it be that the 4th is the control one???