Help understanding when to use resistors

[DVDdoug]

Ultimately, do I need to use a resistor here?

I think so. Is there already a resistor on the little circuit board?

In any case, it won't hurt to enable the Arduino's built-in internal pull-up.

The datasheet isn't 100% clear but the example schematic shows a pull-up resistor and it says:

Device (master or slave) through an open-drain or tri-state port is connected to the data line to allow the device to send data when not able to release the bus, and let other devices use the bus; single bus usually requires an external approximately 5.1kΩ pull up resistor, so that when the bus is idle, the state is high.