I need to replace the fuel tank pressure sensor on my 1998 isuzu hombre.but I don't know where is located at.can you help.is the circuit low voltage.

That sensor is normally located on the top of the fuel tank. That would require draining and dropping the fuel tank. Voltage will be zero at this point because you should have already disconnected the negative battery terminal.
This would be a very big job for a DIYer in the driveway.