not having this system i obviously will be making a educated guess,
looking at this document
- small form factor models – the port is near the edge of the board
- Tower models – the port is between slots 3 and 4
http://h10032.www1.hp.com/ctg/Manual/c04293195
note the z230 illustration, it shows the 2 wires from the motherboard board connector labeled E102 go to the pins on the edge of the card this narrows down the possible connections as it will be only 2 pins so the question is which pin on the board to which pin on the card (only 2 ways to connect so you have a 50/50 chance to get it right the first time) also does the header short any pins? i would guess it does not
i suspect the 2 wires are sync signals or sync/ground if one is a ground, this can be confirmed using a multimeter simply touch one pin on the e102 to a known system ground and if it has continuity it;s a ground connection