HELP: Check engine light after start, scanner shows nothing, turned off after next start

Hi!

I wish I had a better way to described the issue. I have a scangauge that I use for the occasional DTC (usually related to fuel mix, down here in South America, fuel sucks) and also a Bluetooth OBD2 dongle that I used to use for real time data. NEITHER shows any DTC errors after the check engine light is on, and once I stop the truck, the check engine light will go back to off and still not show any errors.

However, once I start driving my toyo, 200 meters into it, it will go back to turn itself on.

I used the bluetooth dongle and performed a scan RIGHT when I thought the light would turn on (based on my previous experience) And got a weird:

C1D20 ERROR, but then just like the light, it went away. i couldn't find any errors like it online.

Anybody had a similar issue?

My truck is 2007.