Correct, lefty. Almost all of this type sensor are ground referenced but a quick test will ensure that that is the case.
Once that is determined for sure, I would check to see that the sensor voltage doesn't exceed 5V. If it is a thermister, the highest reading will be when it is cold.
Then, obviously, the terminal that is positive with respect to ground goes into the Arduino. OP has already successfully wired up an exhaust gas temperature circuit so much of this he may already know.