The number one thing you can do to help the DPF survive is...replace the injectors. Hinos don't look at differential pressure across the DPF to decide when to do a regen, instead it calculates how much soot is being produced by looking at fuel injection quantity. When the injectors lose some of their precision, the ECU loses control of how much fuel is injected, so this soot calculation becomes inaccurate and the soot load in the DPF increases. Regens get hotter and hotter until the DPF's ceramic substrate melts.
There is a test that the dealer can do to test injectors individually. You can also monitor injection quantity at various rpms to get an idea of where they are health wise. Or you can look at the historic high DPF outlet temp saved in memory. 1100-1200F is normal. When you hit around 1400 things are starting to go wrong. 1490~ is when things start to melt and soot escapes past the DPF.
Your truck has a burner system for DPF heating. Burners were made famous on some Mack garbage trucks because they broke all the time and were very unreliable. Initially, the burners on Hinos weren't much better, but they did a recall on the igniters to ones that had slightly longer electrodes and that helped immensely. They also released a number of software updates that helped quite a bit, too. The updated software did things like if it doesn't see flame temp increase immediately at the start of burner operation, it would shut off the fuel and turn the igniters on for a long time to clean the surfaces of the electrodes. The burners still need periodic maintenance, and injector health plays it's part with burner reliability.
The burner has a number of failure modes. Whoever is working on it needs to be familiar with them. Or at least has the troubleshooting guide and factory software and can read and follow directions. Here's my experience with them:
The atomizer develops an internal fault and doesn't turn down the nozzle pressure correctly. Sets a P2436. Roughly $1800. It's mashed into a small area and replacing it can be frustrating. Atomizers also leak fuel, and fuel leaks are a DOT violation so it can't be ignored. It is (barely) possible to get the cover off of it to replace a cup seal and o-ring that are available. There is a TSB that shows the repair and lists the updated parts needed to fix the leak.
There's almost always oil getting introduced into the intake system, either from the crankcase ventilation or from the turbo leaking oil. This is usually not a big deal but this oily schmoo gets in the combustion air valve and it gets stuck. If it gets stuck when it's trying to do a regen, the flame is smothered because there is no oxygen. It gets soaked with fuel inside and when you do get that thing to light off the smoke show is incredible. Like a military grade smoke generator. I'll look for pics. A CAV is $800~.
Sometimes the mantle inside the burner breaks, effects of thermal cycling and vibration. The burner is kind of like an engine, it needs air, fuel, and spark. But it also needs a combustion chamber. So when the guts of this thing break there's really inconsistent, low temperature flame. This part is $3000, but I found out that you can just cut the welds with a plasma cutter, pull all the guts out, then MIG weld everything back together. Works great. Takes 1 hour. You don't even need to take the burner out of the truck. I've done dozens and none have re-broken, years later.
The igniters can get covered with goo that makes them short out, especially on trucks with lots of oil going into the intake. Crappy injectors causing extra-sooty exhaust does not help AT ALL.
The flame temp sensor sees the most brutal temperature extremes, so it fails regularly. They will usually last 150k but after that is anyone's guess. 99% of the time when they fail they go open circuit and that temp is recorded in the event log in the BCU, so it's easy to diagnose. I saw one do the exact opposite thing just the other day. First time I'd ever seen this. Suddenly the flame temp read 7 degrees. Nearby sensors were around 900.
The only time I've ever personally seen the burner's ecu (BCU) fail is when it's been smashed in an accident. Don't let anyone try to sell you one unless they have concrete evidence that it's bad.
I've never seen a burner fuel pump fail. I've seen the burner's fuel filter replaced with the engine's bubbler filter, which is a huge no-no. And I've seen them replaced and filled with the wrong fluids, like ATF and engine oil.
This sounds like a major nightmare but most of the time it works correctly. Healthy injectors will be a huge bonus.
Every 75K take everything off of the face of the burner and clean everything. Swap the position of the igniters so they wear evenly. Check the air gap. Spray carb cleaner through the burner nozzle. Don't mash the soot into the tiny holes in the face of the nozzle. Use a backup wrench with the little braided line for the burner nozzle. If that line kinks it's done for. No need to hamfist it, either.
The worst thing about Hinos is their needs are different than domestic brands of trucks, and the people working on them may realize these differences after they've mutilated it. I get all kinds of work from the neighboring dealerships after some pretty whopping mistakes.
Wow, that is a wall of text.
