I had this exact same problem. Turns out that the aftermarket ground kit I installed didn’t ground the engine as well as oem. Added a ground to thermostat and put the oem trans ground back on. Problem solved.
Im having a similar issue the temp gauge spikes to hot as soon as i turn it on but the motor is healthy and deff not overheating im thinking about just running a after market temp gauge
I found this on the web.. might be your alternator... www.crvownersclub.com/forums/14-problems-issues/35633-overheating-engine-not-need-some-opinions.html#/topics/35633?page=3