Noctua NF-A12X25 FLX 3-pin . . . a 3-pin fan will not throw the diagnostic startup error. . 
My top 120mm fan occasionally exhibits a loud grinding noise that last for 5-10 minutes.  Load doesn't seem to matter.  I've had good luck with Noctua fans in the past where I mounted them in the front of my XPS systems.    Anyone replace their top 120mm fan with a Noctua or other brand?  Looking through Dell support the only cooling related part they sell is the power supply.  Before posting I did see some posts where apparently Noctua fans cause POST errors in Dell machines but otherwise work ok. 
XPS 8920/30/40/50 compatible top fans