Thanks, I found the solution. I plugged the tach cable from the cooler into the cpu_fan header and the error went away, the tach cable is 3-pin but had only one wire, so when plug it into the 4 pin socket of the cpu fan header on the mb, I made sure that wire goes to the yellow (2nd from the left) socket.
  The cooler came with  a 120 millimeter Corsair SP Series PWM fan which spins between 600 RPM to 1,700 RPM, when plugged into the cpu_fan 4-pin header, startup shows the error 2000-051 cpu fan error. I tried plugged it into the top_fan header, and leave the cpu_fan header unplugged, same error, then I plugged in the original cpu fan into the cpu_fan header, the error went away. Now the questions is: I want  cooler fan to be controlled by the cpu temperature, How can I achieve that?   I read all relevant posts I could find on this forum. This post installed the same corsair h60 cooler in 8930 and did not mention any fan issue One post said "Non  DELL fans will have that error due to wiring issue OR too low RPM. " XPS-8930-SA-CPU-fan-failed-to-respond-correctly  I looked at the OEM fan's wiring, it is blue-yellow-red-black, seems to be quite standard. Any other way to confirm? The fan speed could be the culprit here too, but I checked the OEM fan ( 03VRGY)'s spec, its maximum speed is 1700 rpm, so water cooler's fan is between 600 RPM to 1,700 RPM, looks ok to me Any help is greatly appreciated!  
XPS 8930, error 2000-0511 with Corsair AIO's fan