What Is the Function of the Diesel Particulate Filter?

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What Is the Function of the Diesel Particulate Filter?

The diesel particulate filter, or DPF, is classified as an exhaust after-treatment device. It traps ash, soot, and other undesirable particulate matter that remain after engine combustion to reduce emissions. Those emissions create black smoke, which reduces air quality.

What Does a Diesel Particulate Filter Warning Light Mean?

Diesel particulate filters can become clogged with long-term use. This is particularly a concern if you do a lot of driving over short distances at low speeds because the DPF needs higher speeds and longer distances to clean itself. Other causes of DPF clogs include:

  • Incorrect filter installation or modifications to the exhaust system

  • Using the wrong type of motor oil

  • Poor servicing and maintenance, especially of the exhaust system

When a DPF becomes blocked, an orange warning light should show on your dashboard panel. The DPF then goes through both passive and inactive regeneration processes on its own as you drive (illuminating more lamps on the dash) that should restore filter function. Once the regeneration process is successfully completed, the orange light on the instrument panel will go out again.

Sometimes, however, the regeneration process doesn’t work. In that case, it’s time to see your diesel mechanic for advice.

Because the cost of installing a new DPF is high — occasionally more than the value of an old truck — it’s important to maintain your exhaust system properly and ensure your DPF is functioning correctly.

What Does the Diesel Particulate Filter Pressure Sensor Do?

The DPF pressure sensor is part of the mechanism that signals the DPF to undergo a regeneration process. It measures diesel particulate filter air pressure (exhaust backpressure). These sensors can sometimes fail, causing the regeneration process to also fail. This can create excessively high temperatures in the exhaust, which can have disastrous effects on the vehicle, including starting a truck fire.

It’s essential to have regular maintenance on your exhaust system to check that the DPF pressure sensor is functioning properly. If it’s not, it will show up as a code when your mechanic runs the vehicle’s computer system. Early signs of DPF pressure sensor failure include:

  • High engine and/or transmission temperatures

  • Poor performance and fuel economy

  • Check engine light illuminated

  • Black soot emanating from the exhaust


What is Limp Mode?
A diesel particulate filter (DPF) can occasionally get clogged, even during regular driving circumstances. This can lead to the illumination of an engine management light or the generation of a fault code. If this issue is neglected, the vehicle might enter a safety limp mode, which restricts the engine’s speed to safeguard against potential engine damage.

What is a NOX Sensor?
A NOx (nitrogen oxide) sensor plays a crucial role in diesel truck engines by detecting NOx levels and aiding emissions control. When it malfunctions, it can lead to issues like rough engine performance, increased fuel consumption, and even engine derate or “limp mode.”

What is SCR?
Selective Catalytic Reduction (SCR) is a emissions control technology employed in modern diesel-powered vehicles and equipment to reduce nitrogen oxide (NOx) emissions. The SCR system consists of various components integrated into the overall emissions control system.

What is Ad Blue?
AdBlue is a clear mixture of demineralised water and pure urea (32.5%) and is also referred to as Diesel Exhaust Fluid or AUS 32. It is designed to reduce harmful emissions of nitrogen oxides (NOx) from diesel vehicles to non-hazardous gases, in order to comply with more stringent emission standards.”

What is a DEF Heater?
All DEF (Diesel Exhaust Fluid) systems require heating elements to prevent DEF fluid from freezing at temperatures less than -11 degrees Celsius. DEF Heating Pots are designed to swiftly return DEF to liquid form, ensuring proper flow through the lines and pump unit. If your diesel vehicle is operating in limp mode or is not running at full power, a common cause could be a malfunctioning DEF heating element.