Jeep Repair: Wrangler Temp Gauge Reading, hot day today, o2 sensors

Question
My 2005 wrangler 4.0 normally shows a temp of slightly above 210 degrees when running on a hot day. Today, on a very hot day, I was at a stop light, the Check Engine light came on and the temp gauge was at 260 degrees. I watched it for about 10 seconds and the reading went back to 210+ and the Check Engine light went off. I don't think the engine could physically cool down over 50 degrees in 10 seconds, so I question that the problem is mechanical. I had the temp sensor replaced when I had bad O2 sensors replaced a few months ago. What are things to check for high temp reading? Specifically what wires to look at if electrical. Or could there be a mechanical/cooling problem after all, even though the reading resolved itself in only a few seconds? Could a the car computer be going bad and cause such a reading?

Answer
First, I'll assume you meant that the "Check Gauges" light was on since that would better fit your condition. My first suspicion would be that you have sticky thermostat. Change that out first and see if it overheats again. I would not jump to any conclusion that the problem is electrical until that is done.