HELP! PO706 transmission trouble code

My saturn has the P0706 Transmission Range Sensor Circuit Range/Performance trouble code and I dont know how to fix it. Is it a sensor that I replace if so where can I buy one? I dont like taking my car to the shop I rather fix it myself and this code is keeping me from passing emmisions. This code also makes my service engine light go on and then it turns of after a day and then the next day after that it turns back on. I have a 1996 Saturn SL1 with 124000 miles.
Thanks for your help.

the problem may be one of three things: a bad sensor, bad wiring or a out of adjustment sensor. proper testing requires a digital multimeter and a wiring diagram(the Hanyes Manual has a good wiring diagram, but it is of a OBD-1 car(91-95) so it may not match up exactly.