DPFs need to regenerate (empty) themselves. Problems with regeneration may be caused by a town-based, stop-start driving style. Other possible causes include wrong oil type, incomplete combustion, and a low fuel level.
What can prevent normal regeneration from taking place? The single biggest cause of incomplete DPF regeneration is the duty cycle of the vehicle. Engines need to achieve extended periods of high temperature, high RPM activity in order to complete a DPF regeneration.
There are two main types of DPF regeneration: passive and active; however, DPF regeneration can be performed manually using a scan tool. Passive DPF regeneration occurs naturally during normal driving conditions when the temperature of the exhaust gas is high enough to burn off the particulate matter.
A warning light letting you know your DPF is blocked should not be ignored, but can in many instances be remedied by driving in a way which initiates passive/active regeneration of the DPF. Driving for over 10 minutes at speeds in excess of 40mph will often be sufficient to clear the blockage and regenerate the DPF.
A DPF Filter that is too full or not properly functioning threatens both the environment and the truck. The engine can derate when a needed regen does not occur, potentially causing downtime by leaving the vehicle in a state that is either undriveable or in “limp mode” where it can only operate at slow speeds.
Here's how to look after your particulate filter
All you have to do is get your car on an A road or motorway on a regular basis, such as every 300 miles. You then need to run it for 10-20 minutes at speeds in excess of 40mph. This will heat up your exhaust and burn off any soot in the filter.
How Often Does DPF Regeneration Occur? Active regeneration happens roughly every 300 miles and is triggered by your car's electronic control unit (ECU) once your soot level is approaching 40 to 45%. Passive regeneration should occur when you take your car on longer journeys at higher speeds.
Sometimes, a hot and pungent smell can also start coming from your engine as the soot is being burned away. Your stop / start function may also deactivate. Driving for 15 minutes as speeds above 40mph should provide your DPF filter with enough heat to burn away the soot by itself.
As a functioning DPF is vital for a functioning exhaust system, blockages can have knock-on effects that cause your engine to perform poorly. If your engine cannot easily vent exhaust because of a blocked DPF, then it will struggle to cycle, reducing the power output and acceleration of your vehicle in extreme cases.
How to unblock a DPF? 1) DPF Regeneration - Find a motorway near you where you can drive at 70+ MPH for 30-45 minutes; this should provide the optimal conditions for the regeneration process to complete. If this works, consider a regular drive along a motorway regularly to allow the regeneration process to complete.
An automatic regen does not require any action by the driver, other than making sure the truck stays ON. It is safe to continue driving as normal. A regeneration cycle typically takes between 10 and 30 minutes to complete.
However, if the DPF light remains illuminated after attempting a manual regeneration the filter will require professional cleaning. If your vehicle has switched to 'limp' mode it will not be possible to regenerate the DPF filter automatically and will need to be professionally cleaned.
If your forced DPF regen lasts closer to an hour or continues beyond that, it likely suggests that your exhaust temperatures are not building up high enough to successfully burn off the soot collected in the DPF and that the truck is still trying to bring down those soot levels.
If the journey is too short or the vehicle does not have enough fuel the DPF regeneration process might not work. To allow the DPF to regularly regenerate it's advised the fuel tank is more than a quarter full, otherwise, the vehicle will opt to save fuel instead of redirecting it for DPF regeneration.
While your vehicle won't stop running the moment the light turns on, continuous driving can lead to more severe issues like decreased fuel efficiency, reduced performance, and in the worst case, engine damage. An illuminated DPF light will cause an MOT failure.
A DPF can last up to around 100,000 miles if maintained properly. After the car has exceeded that mileage, you could be looking at paying a large amount of money for a replacement - so always properly check MoT and service records when buying a used car.
An active regen cycle is a normal process that takes place as the truck is going down the road. A computer sensor monitors the DPF and a dashboard indicator light notifies the driver that the regen is taking place, or the DPF is now cleaning. “You'll notice a reduction in power during a regen,” notes Nace.
A forced regen occurs when soot builds up inside the diesel particulate filter (DPF) to the point that the vehicle is no longer operable. When this happens, a driver has to pull over and initiate a self-cleaning process that can take up to 40 minutes — valuable time that could have been spent on the road.
A DPF regen, or regeneration, happens when the DPF burns the accumulated soot off its face to prevent clogging. Your commercial truck can carry out either passive DPF regens or active regens.
If it gets bad enough, a dusty air filter can cause damage to the engine, catalytic converter, DPF filters, oxygen sensors, and other vital components resulting in costly repairs.
Unfortunately, the soot (or particulate matter) which has accumulated in the filter leads to clogging and decreases in efficiency. You'll therefore likely come across terms like 'DPF regeneration' or 'burning of the FAP filter' when looking for information about diesel particulate filters.
You are not likely going to be harmed. Your engine, however, is another thing. If you ignore the DPF light, and you continue to drive in your usual “gas/brake” pattern, you will probably end up seeing other warning lights come on. Then, you will have to see a mechanic for what is called “forced” regeneration.