2002 Saturn SL1 Engine Idles high but there is no check eng

My Saturn has been idling at around 2k rpm recently whenever I come to a stop. If I shut the engine off the idle drops down to a normal level. There is no Check Engine Light. I did run the diagnostic on it, but the only message I got was about a mismatch between the water temperature sensor and the actual water temperature.

Since I do not have any check engine light warnings is it possible that I have an onboard computer issue? What physical things could I check to figure out why it's idling like this?

Thanks in advance,
Thad