If this is a US model it is not add on air. Since you know where these sensors are, you should be able to trace the wires using an ohmmeter point to point. Put one lead on the disconnected clutch wire, then probe to the low pressure switch (or whichever switch it leads to next)and learn which one leads there. Then put the ohmmeter lead on the other switch wire and probe with the other meter lead to find where it goes.
It's always about ten times easier with proper schematics, but I've found that if the schematics are close but not accurate they can cause more frustration than good.
Best of luck,