GPIO Input Configuration

Wanted to post a final update in case someone searches for this issue later. The reason the LED was lit constantly was because of some kind of transient voltage around 0.94V that was present in the input pin and was enough to light the LED and barely enough to tigger a logic high in other things I tested like a multiplexer. The issue, however, went away completely once I read something about unifying the grounds between your input and output devices. I went ahead and hooked up the range sensor via a level shifter (since it runs on 5v logic) and once everything was tied together and grounded the problem went away completely. Hope this helps some poor engineering student in the future.