1998 F150

I recently had a check engine light come on. There was no change in performance of the truck. Had no rough shifting, no automatic changing into Drive. Nothing like some of the things I had read that could occur with this error code. I went to the auto parts store and had the code run and it appeared as P0705-Transmission Range Sensor PRNDL Input. At first, I reset the computer on the truck to see maybe if it was an error but after a second start of the truck the error did reappear. I then did the research with the helpful assistence of the parts man at my local NAPA auto parts store and found the correct TR Sensor/NSS. This was replaced. I noticed no change it performnace. Everything was fine before and remained fine after replacing the part.
Again, the light stays off this time until the third start of the truck. Check engine light reappears again.
I have checked and re-checked the fluid level and is perfect. I disconnected the battery last night and then re checked my work, check wiring - all appears ok. I disconnected the harness where it plugs in to the TRS and cleaned more and also blew out with air from compressor. I had re connected the battery again. The light has stayed off but have only ran the truck once since so will wait and see if the light comes on again after work today. I was hoping that it was maybe a fluke and would stay off one of these times. What else could be the problem here?? Keeping in mind that the vehiicle is driving just fine at this point, anyway.
Any help would be greatly appreciated.
Thank you in advance!!!