Valves can be identified by the valve numbers that are on the wires going to them, and the valves have the manufacturer's part number on them (like CS-2105-20).

See this article for views of the valves,
PPC4, PPC3, PPC2+, PPC2-AF - Valve inspection

If you have a leak, it is most often the VENT valve (5) or a down valve (3 or 4) that is leaking.

For Fluke part numbers (from valve numbers and manufacturer part numbers) contact the Fluke Pressure Calibration Technical Support team at pressuresupport@flukecal.com or create a new Case at my.fluke.com/

Q-RPT module valves are not shown but are as follows:
Valve 7 - Low Q-RPT vent valve (protects low Q-RPT is valve 8 leaks)
Valve 8 - Low Q-RPT isolation valve (closed when hi Q-RPT is being used)
Valve 9 - TEST(-) vent valve. In normal operation with BG or G Q-RPTs, this valve is closed during fine pressure control.

PPC3 Manual can be viewed or downloaded here,
PPC3 Manual on Fluke website