The sensor is located inside the wash bottle, at the side. You get access to it...with difficulty...from within the wheel well if I remember correctly.
It consists of two parts... a floating piece with a magnet attached that swings over to a second section that has a contact in it... I am not sure if this is a Hall Effect transistor or just a Reed contact. Do not confuse this sensor with the pump assembly that has the two water pipes attached.
My floating bit has come off and floated to the top of the fluid tank where I retrieved it...I will re-fit it sometime but in the meantime I do not have any error message such as low washer fluid so I need to remember to keep the bottled reasonably filled.
You can try disconnecting the plug but rather pull out the whole sensor assembly to see what is going on.
