IIRC, I paid less than $100 for the actuator from the dealer...and it failed again 2 years later.
It is easy to diagnose the electrical side, just check for 12V at the connector, in 4wd, ignition on, but not running.
I think (not sure) you can check the actuator out of the truck with 12V, and measure the distance the piston travels as it heats up.
If that checks out, check them together, corrosion in the wiring may drop the voltage too much to heat the actuator. Check every connection, and follow the wiring with a digital VOM (both + and -).
I considered the "cable upgrade" but returned it before I installed it, as I had concerns about it surviving the salt here on the shore, and salt on the roads in the winter. It was about $40 more than the dealer part, plus shipping, less sales tax.
Let us know how you do, and good luck.
03 Taco (Gone, and missed...)
88 FJ62 3FE, auto, etc. Sold
07 DL650, lightly farkled