I explained the regen process in another post a while back. Search for it. It's a simple system for the most part but Kubota's way of describing it is a joke (putting it lightly). I wish I could do a youtube vid of each of the dpf soot levels and what the tractor thinks of them, and what input is needed from the operator. But I can't because, well, I don't have enough tractors in the different soot levels to do it.
Level 1: DPF light on, raise RPM light is on below 2200 RPM (on 3301 and 3901).
Level 2: DPF light on, raise RPM light is on below 2200.
Level 2.5: DPF light on, RPM light on, parked regen light on, beep every 5 sec.
Level 3: DPF light blinking, RPM light blinking, beep every 5 seconds, parked regen light on, slight engine power reduction (I think 75%).
Level 4: all lights on, code set in the panel (where the hour meter is), engine power is reduced to 50%, beep every 3 seconds.
Level 5: All lights, code in dash, beep every second, severe reduction in engine power, cannot be regenerated, period.
On level 3, it can be regenerated but only a parked regeneration. Level 4, MIGHT be able to do a parked regen. Level 5 cannot be regenerated at all, will need dealer to remove/clean (or perhaps replace) the DPF, then use diagnostic software to re-set the DPF system. Some dealers don't do the re-set but they better be doing it....if nothing else but to avoid a repeat failure.
Purpose for the power reduction. When the DPF gets real dirty, the pressure-and HEAT-in the engine becomes high. The excessive heat can actually melt pistons. So Kubota decided in order to protect their engine internals to reduce power output at higher soot levels. And it works good for it's purpose, even though it's a pain in the back side from a consumer's point of view.
So what am I saying? If you hear a beep, stop, read up on it, and then make it regenerate. Usually just raising the RPM to 2200 or higher will do it, I go full throttle and walk away from it for about 10 minutes or so while doing yard work or whatever, and by time I'm done, the tractor's done regen'ing.
When the tractor wants a regen, the light comes on and blinks, usually along with the RPM light if the tractor's RPM is below 2200-ish. Simple. When the light's blinking, just raise the RPM, give it a minute or two, the lights will go on solid (in other words stop blinking), and at that point don't shut it off, just leave the RPM high until the lights go off. Once they go out, the regen process is done. I recommend not interrupting it if at all possible because doing so can cause the soot level to increase, possibly to the next level (from 3 to 4 for instance) which might affect whether or not it can be regenerated normally. If you're for instance bush hogging, your engine speed is going to be high anyway. You may see the light come on, don't panic, just let it stay on while you work. Once it goes off, it's done and you don't need to do anything else. This is called a passive regeneration, and takes about half as much time as an active regen-which required operator input (pushing a button, raising the RPM, etc).
That's the simplest way I know of to describe it without overcomplicating it, or explaining like kubota does-in "Jinglesh" or "Japanenglish"-which is the language that they use to write their manuals. They are originally written in Japanese, then translated-hence the complications and the sometimes weird terms like "reray" (relay) or plus cord (positive battery cable). Some of them make me chuckle a little.
