ECUs respond differently. There’s no harm in trying since if the ecu responds by leaning out the mixture then you’ll confirm that the issue is that sensor. Usually the machine will try to work without the sensor but it’s not possible for it to run well. If it were working then it would probably die on the spot. In cases like these the atvs ecu isn’t very advanced you can unplug things one at a time and if you get lucky and there is a positive response then that sensor is probably the culprit. Kind of similar to how people test coils on a car. I’ve had some luck with it but again it’s not full proof. I’m more then certain it’s not the fuel pump though. The only issue you can get with them is weak pressure, since your machine changes how it acts with temperature it kind of eliminates that factor. Gasoline dosen’t get harder or easier to pump with temperature. If you want to eliminate the pump factor just make sure it pumps into a cup and if all else fails replace it if you couldn’t have gotten a tester on it but it’s a rare day to see a pump go on atv. I’d recommend testing a handful of sensors your can get to easily. First take them and read them even though the temp isn’t optimal, if there is one that is very off you found it. You can also just bring them into your house and let it sit for a day and test them. When I used to test electrical components temperature really didn’t matter unless it was too a extreme (low 10 or high 100) even then it would barely affect the reading. Again what you could try is just blocking off the fuel rail and for safety unplugging the injector, making sure it still sparks and then getting it to run off starting fluid or gas in a squirt bottle. If it fires off and you can get it to rev then it means your issue is a sensor in the throttle body. Remeber that without the fuel to the injector, the efi is basically deemed useless and by shooting fuel down the throat your doing what a carbeurator would and your now the only source for fuel. The engine could care less aslong as it gets gas and the ecu dosent cut the spark if one of the connectors isn’t plugged in. I use this method a lot in diagnosis so you could give it a try if you want, can’t really harm anything. The more you find out about the issue, the faster you can fix it when parts roll in.
Edit: If you want to try what I said you probably only need to unplug the injector rather than blocking off the fuel. Pretty easy trial.
