Wipers and sprayer pump

Start by measuring the voltage on the wiper motor. Specifically, put your meter's negative probe on the battery's negative post or on the engine or body, then put the positive probe right on the motor's metal housing. If you find any voltage there, you need to add a ground wire. The motor is bolted to a metal plate that is mounted on vibration-isolating rubber bushings. One of them has a ground strap, but that can arc away near the mounting bolt and cause a broken connection.

Did you check for voltage on the motor housing? If you do find it there, that only proves the motor is good, and replacing it won't solve the problem. The ground strap is where the grounding problem originates. That is on the motor's mounting plate. The fix for this is to attach a new ground wire between the mounting plate and the body.

In case it wasn't obvious, I should have mentioned the wiper switch needs to be in the "low" or "high" position so voltage is being fed to the motor. You should have 12 volts on the purple wire when in the "high" position, and 12 volts on the yellow wire any time the ignition switch is on. If that is when you found 0 volts on the motor housing, the ground wire is not the problem. There is a thermal circuit breaker in the motor that could be defective. They cause more problems than they prevent, due to arced contacts.

Keep me updated on your progress.

Dandy. The engineers found the need to add a pile of electronics to the motor assembly. In the past we had a washer switch that, when pressed, forced the wiper switch to turn on mechanically. Now they turn the wiper motor on electronically when the washer switch is pressed. They found a solution where there was no problem, and added a lot of unreliability in the process.

Happy to hear you solved it.