4th Clutch Oil Pressure Switch
WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The 4th clutch pressure switch is located in the hydraulic passage to the 4th clutch. When oil pressure is supplied to the 4th clutch, the switch is grounded, LOW. When oil pressure is not supplied, the switch is open, HI. The PCM receives the signal from the 4th clutch pressure switch to detect the fluid pressure status, in order to reduce the shift shock when shifting into 4th gear, from 3rd to 4th or 5th to 4th.