ps2cho, using a 17mm wrench, loosen the banjo bolt while the car is running, as locry suggested to me. If there is pressure on the output, fluid should squirt out.

If your car has the same pump as mine (power steering and hydraulic in the same pump 124-460-15-80), the hydraulic section (banjo bolt) is toward the front of the pump, closer to the belt. Removing the air intake hose allows plenty of room to use the wrench to crack the bolt open.

I will post SLS basic function, which explains how the system works at another time for all with the SLS problems, but what locry and ds190 suggested, should tell you if the pump is bad.

Good luck
Michael