PIS stands for Punto di Incipiente Slittamento or, in English, Point of Initial Slip and is a parameter that (in simple terms) tells the TCU where the bite point of the clutch starts. It is measured in mm and would typically be in the region of 4mm to 5mm. The PIS is entered into the TCU when a new clutch is fitted and an algorithm works out how it changes as the clutch wears out. To properly calibrate the PIS you need an SD2 machine (or equivalent).
Having a too high PIS means that the TCU expects the clutch to bite when it doesn’t. This erroneous message causes the TCU to hunt for the biting point and thus “slips” the clutch which in turn causes premature wear. Badly worn clutches can be made to last longer by resetting the PIS.
(From Voicey)
