Hi,
Those resistors were not acting as pullups in that circuit.
Spec sheet is a bit lacking when it says NPN output, normally high!!!
This one is a bit more explanatory, Yes will need to turn pullups ON.
Tom... 
(I found a site that shows the "pullup" resistor as they call it in series with the sensor output, which is contrary to the information table they post in the schematic.)
SHT-015d.pdf (175 KB)