After re-reading some threads it doesn't sound like there is a definitive answer on whether the gauge/message is functional on trucks built without the sensor. Basically just a lot of opinions and observations. Some say the gauge works and they get a display message when a regen is occurring others say that they don't get either or just one or the other. My guess is that they were patching the firmware on the fly to account for the lack of a sensor and they did multiple revisions. Depending on when your truck was built your gauge/message may or may not be functional but that's just another opinion.
The gauge works as advertised on 2022’s,
@Blythkd1 has a unique issue on his. It would be interesting to see if a monitor like the CTS3 picks up his active regens or if the issue is deeper.
If the gauge reads 0% all the time that’s a good thing.
Regens are usually short, and depending on driver, or driving conditions, they may not be noticed either audibly or on the DPF screen.
I know multiple people who swear their truck has never regened because they never noticed it. If the truck has more than 24 hours on it then it’s had a regen, and the 19+ trucks tell you when you’re in an active regen.
Many drivers are just oblivious to the nuances of their vehicles. I’ve been in trucks with drivers that claim they have never noticed a regen and then have been able to point one out to them.
At the end of the day it’s far more likely that people just don’t notice the regen happening, or indications of them happening, instead of them not happening or being indicated.