My earlier diagnosis was flawed; The click I heard when shorting the kickdown switch 12v supply line to ground was not the KD solenoid - it was the ignition relay cycling. At the time of the test I was using a battery charger to supply power, because the battery is out of the car for battery tray R&R. I guess fuse #14 would have blown with the battery in circuit
I traced the black wire from the KD switch; it goes directly to the KD solenoid (rubber boot connector at rear of transmission).
The KD solenoid on my car tests open circuit - measured between the solenoid connector and ground. I plan to replace the KD solenoid when I do a trans fluid change.
Cheers!