Sensors sold by MoTeC in the USA come with data sheets detailing the pinout. You don't show your location, so I don't know if you got this from MoTeC Australia, or MoTeC USA, or elsewhere. Either way, the supplier should be able to provide that information.
For example, you'll find many of the datasheets here:
http://www.motec.com/downloads/downloaddatasheets/(Look in the USA Grail for all the USA data sheets)
If you can give us a part number of the sensor you have, perhaps we can help you find the info you need.
The datasheet for the "M DHALL 437-DTM", shows a DTM-4S on the sensor, with the following pinout:
Pin 1 - Drain (shield)
Pin 2 - 0 volts
Pin 3 - Signal Out
Pin 4 - 8 Volt Power
This same pinout is used for all the other Hall Effect sensors I could find in the USA Grail document.