definitely the sensor happened to me about 3 months ago i changed the sensor myself and everything is fine. here is a link to the part your gonna need.
I recently got a CEL and scanned it with a buddy's OBDII reader. The code it gave me was P0117 which according to the book is "coolant temp circuit low" So I take it the coolant sensor needs to be replaced. Car drove fine while the light was on for the last few days, but this morning it would not start. It would crank, but wouldn't catch and if I gave it gas it died. It would also idle really rough and would sputter if I gave it gas. Is there anything else that could cause the problem or is it the coolant sensor that is bad?