Coolant level low warning light,

like inch or so

 

Could be the magnet in the tanke is getting stuck. May have to replace the entire surge tank if ur still getting a code or low coolant alarm after replace sensor. Also could be one of the wires in the harness is rubbed thru

 

Check out Rusty Cracker on Youtube. He recently had the same problem on a Cascadia. He did a quick fix by using a paper clip to jump the sensor and it cleared his issue for now

 

Wait.

I think this sensor is one that can be unscrewed from the tank, if so take it out of the tank and pull the arm up and see if the code clears. If it doesn't then it is either in the wiring or you have a defective sensor, I've had a bunch if them that were just junk and wouldn't work even brand new.

Your question about checking the oil, I always check it stopped, let it settle for four minutes and check it. If you do it in the morning, before starting the truck, that's the best time.