I know, but to be fair you didn't mention that before! Originally you only mentioned taking out the thermostat to test it with a thermometer...
Not the sensor, which you originally implied was best to test in situ (no mention of testing it against a thermometer?)
Man this is hard work!
All I originally said is "you'll need to take the sensor out to test it", which indeed you will
have to do to measure the resistance
against temperature with a glass bulb thermometer as you quite correctly say in your last post. You don't need the diagnostic tool to do this - I never said you did for this. All I said you'd need a diagnostic tool for was to "check the coolant temperature that the ECU is reading".
Anyway, in a nut shell, I think we have finally established/agreed in a roundabout way that, to test the engine coolant temperature sensor on an XT you need to:
1) Remove it
2) Heat it up in water with a glass bulb thermometer
3) Measure the resistance against temperature