There are several locations - one being the firewall inside, at the Brake/Clutch/Accelerator pedals assembly. Up and underneath at the firewall - in mine it has Black with dark blue/violet stripe (Dark Blue or the Violet is fine line)
One FROM the Body control module - but near and by the module - at the kickpanel on the RIGHT side
One at the floor pan - by and at the seats - requires you to remove trim and the door gasket - to gain access to locate the bolt - in the riser ridge that the front seat bolts - bolt to. IT uses a separate bolt dedicated to the grounding points for several electrical devices in and around the area that includes switches and interior accessory returns.
The above is a schematic, - one of the power supply side - note F15, F13 and F11 are fuses - so check your owners manual and see if these are identified as such - for these fuses power the Rear and Front - and also the Washer motor - but the MOTOR for the washer is a single two terminal - so the Motor runs one way, but when the power to the wires are reversed - it reverses the direction - a type of check valve is used in the washer to direct the fluid to one hose or the other, depending on the port it "gushes" from when the polarity of the motor is in one direction or opposite.
The ground for the Washer is on the firewall just below the windshield - and back at the Body Control Module - but is buried in the harness from the front radiator to the spot on the frame under the battery. Wiper motor - shares the same ground point as the several points the ABS, Brake and even ignition share towards the main ground bond point the Battery uses.
The "C" stands for the Connector - while the "S" stands for the SOCKET/Splice - so there is a Male and Female as well as a "combined" connection type along the route that the wires take.
In this portion, the main front wiper motor shows a "park" signal too - so if ground seems ok, it can also get confused with "Park".
Also note too, that the Front wiper, it has a Ground, yes, but also a SEPARATE connection at the Body Control Module, for Wiper Return - being it too is "Ground sense" - so how this would work is to act as a "sense" if the Ground potentials between the Body Control Module and the Wiper were too different in potentials. Which may indicate a type of jam in the wiper arm - possibly causing bodily injury - from the excessive current draw - or in a stuck position - which then it would force a stop and turn off power to the wipers so they wouldn't cause further damage or further damage to the BCM from that draw and damage internal components even though they are powered thru fused lines.
But you wanted to know about the wiring - so the Wiper motor has a 4-pin connector - just check at the connector, to see if Ground still exists.
IT would also display a message in the APIM if you have one.
Best I can do to help you get started.
