Rear window washer fluid resevoir
It is located on the right side of vehicle, in the rear. Spare tire on the left or mounted outside. Remove the interior cover, should be quick release fastners.
On my 96 it was the same one as the front. There were just 2 pumps on it.
He's right it should be all run off of one tank. If the rear washer isn't working there could be an issue with the line that runs to it or the rear washer pump could be shot
Looking for a Used Jimmy in your area?
CarGurus has 264 nationwide Jimmy listings starting at $4,500.
Search GMC Jimmy Questions
GMC Jimmy Experts