Sensor is is on left engine block (when sitting inside the van), above the spark plugs, with a blue harness. (See attached photo -it's the sensor on top). I have not been able to identify this sensor anywhere else in my Internet search, so I'm hoping you guys can do it!

 

most one wire sensors are temp or pressure sensors. since is so close to the knock sensor its probably a coolant temp sensor or temp switch....unscrew it and seeif coolant comes out

 

That's the one (coolant sensor)! The coolant came pouring out when I unscrewed the sensor (should have had a bucket under the van, though). Thank you so much!