2009 Tundra Blinking 4HI ... finally FIXED. Why did nobody tell me this?

2009 Tundra. Posting this so hopefully people won't go thru what I had to.
After weeks of google searches and changing parts I finally fixed the "not having 4WD / 4HI blinking light.

I changed the ADD Actuator that was corroded to crud and stopped working.
Still wouldn't go into 4WD. Light blinked slow a few times then fast blink.
I'll skip the dozens of things that I tried and parts that I replaced and get to the point.
Turns out the bad ADD Actuator sent 2 fault codes to the ECU. I assume the ECU wouldn't give the "all clear" to the 4WD control module to run the ADD Actuator even after the new ADD Actuator was installed.
There is no way of knowing that there is a fault code because it doesn't trigger a check engine light.
Since I don't have access to Toyota Techstream, I purchased a Carista OBD2 Module thingy that can access the ECU. I think it was $38 and another $30 for a 1 year subscription to the app that runs on your phone.
I ran the diagnosis, it quickly found the fault codes, and I was able to clear them with the Carista. Now the 4WD works as intended. This thing also allowed me to make some changes on my new 2025 Tundra and it's super easy to use.

Hopefully you found this before you:
- Fart around with the transfer case actuators, removing, testing, cleaning and clocking, etc.
- Test every wire from the 4WD control module to the ADD Actuator only to find none are broken.
- Buy a used 4WD control module on ebay and find it made no difference
- Change all your wheel sensors
Or I suppose you could take it to the dealer for them to tell you that somehow a quart of gear oil evaporated out of your transfer case (I'm guessing they just cleared the fault codes for you but they needed to justify your $300 bill)