By: John Tucker
The DPF light comes on to tell you that there’s a problem with your car’s diesel particulate filter. This is something that has been fitted to diesel cars since 2009 to reduce the amount of soot released through the car’s exhaust system, lowering emissions. This soot is harmful and can cause respiratory problems.
Although having one of these filters in your car’s exhaust helps to significantly reduce the amount of soot emanating from your exhaust, it can become blocked, causing the DPF warning light to become illuminated on your dashboard.
When the deposits of soot build to a certain level, the car’s engine control unit starts what is known as ‘passive regeneration’. More fuel is injected into the engine, which raises the temperature in the exhaust system. This burns the soot, turning it into a fine ash and expels it through the exhaust.
Your car usually performs this process whilst travelling at higher speeds, as this is required to maintain a high temperature in the exhaust system.
However, if you spend most of your time doing small trips around town, rarely reaching motorway speed, your car cannot perform this regeneration process. This causes the soot to continue to build up in the DPF, eventually causing the diesel particulate filter light to become illuminated.
When the DPF light has become illuminated, it’s telling you that ‘passive regeneration’ has failed and that you need to actively regenerate the diesel particulate filter.
You can do this by increasing your speed to more than 40mph for between 10 and 15 minutes. This should allow the exhaust to reach sufficiently high temperatures to burn the soot and clear the filter.
During the regeneration, you may notice things like your engine making an unusual noise, a slightly pungent smell coming from the exhaust and an increase in your fuel consumption. This should all return to normal once the active regeneration process has completed. You should also see the DPF light go out.
If you cannot maintain a speed of more than 40mph for long enough to allow the regeneration process to complete, the soot will continue to build up in your filter and your DPF warning light will remain on until you have the problem fixed.
Call us for advice
Technically yes, but we would not recommend it. If you ignore the DPF light and continue driving, the build-up of soot will soon reach a point whereby your car has to enter ‘limp-home’ mode in order to prevent any damage to the engine.
This will probably result in other warning lights becoming illuminated, advising you to take your car to your local garage for diagnosis.
Your garage should be able to perform a forced DPF regeneration, which should clear the filter and allow it to function properly once more. However, it’s not a guaranteed fix, especially if the filter itself has become damaged or other damage has been done to the engine. More serious repairs could run into the thousands, depending on the damage and the vehicle.
It really isn’t worth ignoring the DPF light.
Only by owning a car that suits your needs. If you drive long distances, perhaps commuting to work, then a diesel with a particulate filter would be fine. You would regularly reach speeds required to perform both passive and active regenerations, reducing the likelihood of having any problems with the DPF.
However, if you only do short journeys, perhaps a diesel isn’t really for you. If you only use your car to pop to the shops, or do the school run, a petrol engine is more suited to you. If you ran a diesel with a DPF, you’d rarely give it the opportunity to clear its DPF, resulting in you seeing the DPF light more than you would like.
If you would like to find out about other warning lights, make sure you read our
Dashboard Warning Lights Explained
Please note we record all our calls to ensure that we give you the service you deserve.
We also share information about your use of our site with our social media, advertising and analytics partners
who may combine it with other information that you’ve provided to them or that they’ve collected from your use of
their services. You consent to our cookies if you continue to use this website.
Some of these cookies are essential, while others help us to improve your experience by providing
insights into how the site is being used. For more detailed information on the cookies we use, please
*Your browser is currently set to 'Do Not Track' and therefore some options have been disabled. Please adjust your browser settings to enable these options to be chosen.
The website cannot function properly without these cookies, and can only be disabled by changing
your browser preferences.
These cookies allow our website to remember information that changes the way the site looks or behaves,
so that you can personalise your experience.
We use statistic cookies to monitor page traffic on our website. This information enables us to improve
the website for visitors.
Social cookies allow us to track visits from our social pages and may be used to target adverts based on your social media preferences.
These cookies allow us to understand general customer behaviour and track where you have visited from,
which allows us to monitor the success of our marketing campaigns.
Cookies are small text files that can be used by websites to make a user's experience more efficient.
The law states that we can store cookies on your device if they are strictly necessary for the operation of this site. For all other types of cookies we need your permission.
This site uses different types of cookies. Some cookies are placed by third party services that appear on our pages.
Your consent applies to the following domains: www.stoneacre.co.uk
Cookies are used to analyse web site traffic and are commonly used on the internet to make your browsing more efficient by remembering your preferences and tailoring its operation accordingly. Please be aware that cookies do not harm your system.
These cookies do not give us access to any personal information and although most webs browsers allow cookies they can be turned off if you wish by using your “help” facility. This may prevent you taking full advantage of our web site.