Hello,
I found this on page 8R-26 in the service manual(it is available for download on this forum). For wipers always on. I did not see where you measured a voltage at the wiper switch Mux on your well written troubleshooting word doc. I hope this helps!
Turn the ignition off.
Disconnect the Multi-Function Switch harness connector.
Note: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Measure the voltage of the Wiper Switch Mux circuit at cavity 7 of the
Multi-Function Switch harness connector.
Is voltage present?
Yes >> Repair the Wiper Switch Mux circuit for a short to voltage.
Perform BODY VERIFICATION TEST.
No >> Replace the Multi-Function Switch. (Refer to 8 - ELECTRICAL/
LAMPS/LIGHTING - EXTERIOR/MULTI-FUNCTION
SWITCH - REMOVAL).
Perform BODY VERIFICATION TEST.