July 13, 2021 / by Danny Mavis

Diesel Particulate Filters, or DPFs, have been commonplace in diesel vehicles for over two decades now. They’ve been present in quite a few Toyota models, such as the Hilux, Fortuner, and Land Cruiser Prado, and even though DPFs have been used for quite a while now, not everyone knows how to maintain them. I’ve already talked about improving the Land Cruiser’s performance with an exhaust system, so it’s only fitting that I also talk about DPFs.

What is a Diesel Particulate Filter
Source: brakeandfrontend.com

What Exactly is a Diesel Particulate Filter

Up until a decade or two ago, diesel vehicles were known to have a high rate of emissions, which made them significantly less eco-friendly than their petrol counterparts. In order to avoid having all diesel vehicles taken out of commission entirely, the industry created the diesel particulate filter, which significantly reduced the diesel vehicles’ emissions. They work by capturing and storing exhaust soot, which is the main factor behind the emissions. That’s why they are often referred to as soot traps for diesel vehicles.

However, they have finite storage, which means that the DPF won’t work indefinitely without being cleaned regularly. The trapped soot needs to be emptied, or burned out so that the DPF can regenerate. This regeneration process burns off all of the excess soot that’s still in the filter, which reduces the vehicle’s emission rates down to an acceptable level. This can be observed when the diesel vehicle is accelerating because you won’t be able to see the black smoke that typically comes out of unfiltered diesel vehicles. Using a DPF has become mandatory in the last decade, as they are definitely very useful pieces of technology.

Known Issues with Toyota

Toyota had a long legal dispute over diesel vehicles sold from 2015 to 2019, such as the Hilux, due to faulty or defective diesel particulate filters. Since then, Toyota has fixed thousands of their diesel vehicles, so much so, that the Toyota Hilux DPF is now an excellent system that is trouble-free for the past two years. Some of the main changes to the DPF include changing the design of the so-called fifth injector and diesel oxidisation catalyst, as well as updates and changes to the software that regulates how the technology functions. Since those changes have been made, the Hilux DPF kicks in much more regularly than before with a rate that you can be sure will properly regenerate the vehicle’s filtration system. Even though Toyota used to have significant problems in the past, so much so that they led to a legal dispute, the entire issue is now fixed, and you can expect their DPF to function as intended.

Toyota Hilux DPF
Source: motoringnz.com

What Causes DPF Blockage

No filtration system lasts indefinitely. There are a few things that can cause blockage, namely short drives at low speeds, which is usually the number one cause of DPF blockages. That’s the main reason why diesel vehicles are rarely present in cities. Poor servicing can also be a significant problem because a well-maintained DPF should last at least 150,000 kilometres. There are some oils that can also cause a blockage due to additives, so make sure you’re using one that won’t doesn’t contain any. Even low-quality fuel can significantly lower the entire DPF system’s lifespan, so while you may save on fuel, you’ll definitely have added costs once you have to repair the DPF.

Maintaining a DPF
Source: overdriveonline.com


Maintaining a DPF is done by allowing it to fully regenerate once it’s full of soot, which you’ll know of due to a warning light on the panel. There are two main types of regeneration, active and passive, but in some cases, you can force the system to regenerate, which is called forced regeneration.

Passive Regeneration

Passive regeneration happens when you’re driving the Hilux at long distances and high speeds, which allows the exhaust temperature to rise to a higher level and burn off the excess soot trapped in the filter. This is often considered the main way to clean off the diesel particulate filter, which is why it’s advised to regularly drive your car on longer journeys at high speeds regularly. However, not everyone drives this way regularly, which is why there is a second type of regeneration.

Active Regeneration

During active regeneration, fuel is injected automatically as part of the car’s ECU. It happens when the filter reaches a specified limit, which is typically 45% in order to raise the exhaust’s temperature and burn off the excess soot. However, there are some potential issues with this, such as if the drive is too short, the filters might still be slightly blocked. If that’s the case, you’ll see the warning light showing that the filter is still blocked, so you should continue driving for ten minutes or so at a speed above 65 kilometres per hour.

Forced Regeneration

If you notice that the light is still showing blockage even after trying either passive or active regeneration, then it’s time to have the car checked out. Some garages can have the DPF cleaned up in a process called forced regeneration, and it’s effective at cleaning out the filter 100% of the time. Just make sure to not let the problem linger for too long because the car itself will have issues with performance, and not to mention the possibility of even more damage to the car.

Diesel particulate filters are an important piece of technology that allows diesel vehicles to be fully legal to use. They might be a hassle to maintain sometimes, but with the right care, you won’t even know they’re there.