Symptom: The dryer's control panel would light up; however, the drum would not start. A diagnostic test showed "F4/E4." (Note: This dryer has no history of issues and worked flawlessly for almost a decade prior to this problem.)
I researched the problem online. I found that it could be as simple as a faulty Thermal Fuse (WP3392519//AP6008325) or as difficult as several bad components, to include the aforementioned Thermal Fuse, the Thermistor (WP8577274//AP6013514), and/or the Electronic Control Board (WPW10542001//AP6022778). I erred on the side of caution and ordered all three parts. While they were being shipped to my house, I thoroughly cleaned lint, hair, and other debris from the inside of the appliance after I removed the top, back, control panel, lint screen, lint screen housing assembly, lint duct, door housing, and exhaust pipe. I also cleaned all the parts I removed, and I used my backpack leaf blower to blow accumulated lint through the exhaust pipe behind my dryer and out the vent on the side of my home.
When the parts were delivered, I removed the old Thermal Fuse and Thermistor and replaced them with the new ones. I had plenty of room to do so via the back of the dryer even though all of the online videos I could find showed the fix being done after removing the dryer drum, which I did not want to do. I reassembled the dryer and tested it. Since it had returned to normal working order, I did not install the Electronic Control Board, which was still in its unopened manufacturer's box.. I opted to return it for a refund. (Note: Do not open the box that contains the Electronic Control Board until you are sure that it is needed to complete the repair.)
As a result of this experience, I have learned some very valuable lessons. First, despite having no background with appliance repair, I am very capable of fixing and maintaining the washer and dryer in my home as long as I do the proper online research. Second, I will perform dryer-related lint cleanings about every 18-24 months in the future OR sooner if I notice the that "Clean Lint Screen" light stays red continuously.