This article might be interesting to read, as it goes through the operations and sensors at a pretty low level.
http://www.shrani.si/f/k/4j/4sd9KbkF...hicle-elec.pdf
Code:
Pg 13, Wash Windscreen
On pulling the wiper switch, initially the washer fluid pump is switched on followed by the windscreen wiper. The washer fluid pump remains switched on for as long as the wiper switch is pulled.
The signal is routed from the SZL to the Junction Box Electronics Control Module (JBE).
The JBE activates the washer fluid pump directly. After the pump is switched off, the wipers continue to operate for several wipe cycles in order to wipe the windscreen dry.
The JBE will no longer drive the washer fluid pump if the fluid level in the washer fluid reservoir is too low. The JBE receives the information necessary for this purpose from the washer fluid level sensor.
It almost sounds like the JBE sees a low fluid reservoir and refuses to pass the request for windshield cleaning. However, if that were the case, you'd be getting the low fluid warning.
Not sure if that helps, but it gives more context to the somewhat advanced system and what it is doing when you pull the stalk.