JayMan:
I use that sensor and it has 3 wires. You need a 4.7k resistor between vcc and signal for it to work as well. Plus taking a look at the code will help.
it has 3 pins, but can be wired as a 2 wire device.
without the OP posting code and a pic of his device or wiring schematic, we are only guessing what he is doing