AdBlue® and Car care > Car maintenance & accessories > DPF warning light: What does it mean? How to clear it?

DPF warning light: What does it mean? How to clear it?

DPF warning light

Your vehicle’s DPF warning light has just become illuminated? When this warning light displays on your dashboard, it generally means that your vehicle’s diesel particulate filter (DPF) is clogged. While this type of anomaly should not be taken lightly, several solutions exist to put it out before calling in a professional.

DPF warning light: what does it look like?

Visible on your vehicle’s dashboard, the DPF light is most often represented in the form of an orange-coloured exhaust pot filled with small “balls”. These “balls” symbolise the scale particles (or soot) that clog the particulate filter.

In some cases, the particulate filter indicator may take the form of:

  • a horizontal cone blocked by balls
  • a rectangle filled with marbles positioned above one or two downward-pointing arrows.

diesel particulate filter warning lights

The most common types of DPF warning lights – source: Dash Lights

Note that on recent vehicles, the symbol is usually accompanied by an explicit message such as “Risk of particle filter clogging. Please see handbook” or “Excessive soot levels in filter. Drive until warning light turns off”.

If a message such as “Abnormal soot levels in filter. Have the vehicle inspected” or “Maintenance required” is displayed, you are strongly advised to call in a professional. Indeed, this procedure requires the car to be lifted, a protective casing to be removed, and a dedicated tank to be filled or a flexible bag to be replaced. In addition, the mechanic must intervene on the electronic system to extinguish the error message.

Note: on some car models, there is no diesel filter warning light. In this case, it is the engine light that will be displayed if the filter is clogged.

If you are in any doubt about the format of your vehicle’s DPF warning light, consult its owner’s manual.

Why is the DPF warning light on?

Most of the time, the DPF warning light comes on when your vehicle’s particulate filter is clogged or dirty. It is then necessary to clean it, or even, in some cases, replace it. To better understand this alert, let’s review the role of the diesel particulate filter.

How does the particulate filter work?

The particulate filter is an anti-pollution device that forms part of the vehicle’s exhaust system (it is positioned just after the AdBlue® injector and the catalytic converter). It works in two stages, as follows:

  1. Firstly, the DPF filters the most harmful particles from exhaust gases by trapping them in its cells.
  2. Once the alveoli are full, the filter is supposed to regenerate (or self-clean) by burning off the stored particles.

However, this regeneration of the DPF can only take place if the engine speed is at at least 3000 rpm. This is because it is at this speed that the engine temperature (around 550°C) is able to eliminate the carbon particles. In theory, it is only possible to reach this temperature level when driving on a motorway or expressway.

In other words, if your journeys take place mainly in town, your vehicle’s DPF filter will be more exposed to clogging problems.

For more information: History and operation of the DPF (Wikipedia)

DPF warning light on: what could be the cause?

As you’ll have gathered, one of the main causes of the DPF warning light coming on is short journeys at low speeds, which encourages the build-up of carbon deposits in the filter.

There may be other reasons why the filter has failed and the warning light is displayed on the dashboard:

  • altered combustion as a result of a mechanical problem, which will generate a surplus of particles
  • a problem with the injectors, with similar consequences
  • a DPF leak, which will cause a significant difference in pressure between the filter inlet and outlet
  • a dysfunction of the vehicle’s electronic system.

How do you interpret the state of the diesel particulate filter warning light?

The particulate filter indicator may behave differently depending on the malfunction detected:

  • if the DPF light comes on and off (flashes), this most often means that the filter is clogged or that the pressure sensor is faulty 
  • if the light is steady, then there’s a good chance that the particulate filter is clogged, and therefore can no longer function properly.

Now that you understand the causes of the DPF warning light coming on, let’s look at the solutions available to turn it off.

How to clear DPF warning light?

In the majority of cases, the DPF warning light goes out when the particulate filter cleaning is carried out. There are several ways of cleaning or regenerating the DPF:

  • Drive on the motorway for 20 minutes at 3,000 rpm: the engine temperature will then be high enough to initiate the particulate filter self-cleaning phase. If this method works, the FAP light should go out quickly.
  • Use a DPF cleaner: this additive will thoroughly clean your particulate filter, giving it a second lease of life, and significantly increase your engine’s efficiency. It’s important to follow the instructions carefully to ensure maximum effectiveness. While the price of a DPF cleaner may seem high, you should be aware that it often avoids the need for a professional or the very costly replacement of the particulate filter (between £300 and £1,400 minimum at a garage).

What cleaner should I use to turn off the DPF light?

If you want to clean your particulate filter yourself, we can recommend several products. Currently, the following DPF cleaners are considered the most effective on the market:

  • The Forté DPF Cleaner & Regenerator is highly recommended for its effectiveness and ease of use: add the DPF cleaner directly into the fuel tank and allow the vehicle to idle for 45 min. Then, simply repeat the first method (driving on the motorway at high revs) to start the cleaning process.
  • The Wynn’s Diesel Particulate Filter Cleaner is also renowned and simple to use: the entire bottle should be emptied into the tank, ensuring that it is at least half full of fuel. You then need to drive for at least 10 km, including several times at high revs, before adding fuel.
  • The Redex DPF Diesel Particulate Filter Cleaner: an alternative solution to the previous two, recommended by professionals, which works in the same way.
  • The STP Diesel Particulate Filter Cleaner, which is also an effective solution for cleaning the DPF.

What should I do if the DPF warning light doesn’t go out, even though you’ve cleaned it?

If, despite using these techniques, the DPF light does not go out, visit your garage as soon as possible. Indeed, he will be able to:

  • Carry out an in-depth diagnosis of your particulate filter’s malfunction
  • Clean the DPF or rectify the fault detected (which may be material or electronic)
  • Replace the DPF, if it is too damaged and cannot be repaired.

DPF light on: can you continue driving?

In general, it is possible to drive with the DPF light on, but only for a short distance, as you are exposing yourself to significant risks:

  • switching your vehicle’s engine to “degraded” mode (reduced power and speed, and risk of stalling)
  • significant increase in fuel consumption
  • rising emissions of particulate pollutants
  • deterioration of the vehicle’s engine, or even breakage of certain parts, in the worst case scenario.

So as soon as your vehicle’s DPF light comes on, don’t delay in taking action, following the methods outlined above. This will prevent further damage and costly servicing.

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