Hello;
Pins 3 and 4 of the ICP01 have the purpose of connecting the ICP chip sensor to an on board current source.
Maybe your sensor already has a current source, so when you connect it to pins 3 and 4, both currents actuate, creating a different current value that makes the sensor stop working.
Another possibility is that the module is damaged, however, since you can see good readings when connecting to pins 1 and 2, I don't think the module is bad.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments