Re: It's (almost) never the instrument.
My car, on a particularly hot day, wouldn't start when it was over 35C, or parked under the sun for several hours. But it cranked on a cold day or early mornings, no problems.
A thermocouple was reading *minus* 68C. 68 degrees BELOW freezing, under the scorching sun. It told the ECU to soak the engine in gasoline, because it thought it was a cold day. It smelled like a carbureted VW Beetle. The ECU was working with faulty sensors, but it was behaving correctly.
Instrument failures produce impossible readings, and I can verify that.
The dealership wanted me to buy a new ECU and the entire eletronic fuel injection system again. A dedicated, attentive mechanic with the intrument reader attached to the car saved me over 500 bucks.
By the way, that sensor was tucked under the car for 19 years without maintenance before failure. You gotta love Honda for something that can work 19 years before failing.