Ok , I found the P/N in Rocky's posted file.
The sensor , mounted on top of the cylinder, MUST ! only be replaced with the jack fully retracted, so there is no hydraulic pressure in the system . Make sure the area around the sensor is clean , so no debris can be knocked into the hole, while it's out. The sensor isn't grounded through the threads so seal tape can be used.
Access could be limited by your particular installation, you may have dis-mount the jack and drop it slightly for better access.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.