I know next to nothing about the 2.5 XJ's, they are really rare here. First off I'd inspect very closely that the wiring for the CPS or any wiring for that matter, didn't get caught between the bell housing and the motor (seen it more than a few times).
I don't have a 96 FSM so I'm really guessing here. Unplug the CPS and check the voltage with the key in the run position. If there is no change it is likely another sensor (or wire) is shorted and sucking the voltage down.
On the 97 L6 motor the same 5 volt orange wire supplies voltage to the cam position sensor, the MAP and the TPS. Unplug them all and see if the 5 volts comes back. If there is no orange wire going to the MAP or TPS, you likely have the earlier configuration. But unplugging sensors and seeing what happens to your CPS voltage isn't a bad strategy anyway, the various supply voltages to different sensor sets is interconnected someway inside the PCM.
It may not even be 5 volts, I´m not sure if the 2.5 is OBD 1 or OBD 2 and/or basically a 95 configuration or a 97 configuration.
On earlier models (95) the CPS shares the (orange wire) supply voltage with only the cam position sensor and the speed sensor and is an 8 volt supply.
Just trying to help, hopefully I didn't just confuse things.
Just a thought, but I've seen guys pull and reinstall the tranny and smack and crack the CPS while reinstalling the tranny/bellhousing.