A sensor is a device that converts some physical parameter into some type of electrical or electronic signal that a computer program can recognize. And as such, some physical parameter/s are inputted a precise rates to obtain a corresponding precise electrical/electronic output.
Back in the 80's automotive companies started hiring attorneys because of liability laws, if you didn't know this a good portion of the cost of an automobile goes toward attorneys paychecks and insurance. Was so bad, I could not even talk to another head engineer at another department unless an attorney was present.
Another thing attorneys did was to prevent the vehicle manual department from listing testing specifications of all these sensors. What parametric inputs with corresponding outputs numerical values as would be subject to warranty replacement. Engineering department would provide all these specifications.
So what does a manual tell you since then? Replace with a know good sensor, essentially from an identical donor vehicle that seems to run okay. True is, you don't know if that sensors is good or bad or whether the information its receiving is the culprit.
Talk about the blind leading the blind! Was involved in designing distributor less ignition system, EPA requirement so a user could not screw it up. Just had to remove the timing marks on the harmonic balancer.
Not one of mine, but a sensor was mounted under the harmonic balancer on a bracket that was bend. Had to mark my own timing marks to properly adjust it. PITA!!!
"...the ECT jumped up to 82 and then 85. It would fluctuate up and down..."
The ECT rising that you described recently sounds fairly normal, but a significant "fluctuation" would not be.
When I pulled up the live data, the ECT was more erratic.
the next time I started cold and took readings every minute, it progressively went higher compared to the IAT.
just got home from work and IAT was 48 and ECT was 52.
MAP started out at 29 and dropped to 11 until it started and it stayed there.
now after running for about 3 minutes, ECT is 113 and IAT is 52.