In a diesel vehicle, the DPF light can become illuminated on the dashboard to warn you about a problem with the diesel particulate filter.
A diesel particulate filter (DPF) is a feature of all modern diesel vehicles exhausts, it reduces the amount of diesel black soot emissions which has been found to contain several harmful substances.
Having a DPF in your car or commercial vehicle will reduce the amount of soot being emitted from the exhaust, however, over time it can become blocked and the DPF warning light will show on your dashboard.
What does a DPF warning light look like?
A DPF warning light is a unique icon that is separate from a check engine or other warning light. In most mainstream manufacturer vehicles, a DPF warning light looks like dots surrounded by a rectangle or exhaust shape.
Depending on the make of car, a DPF warning light can either be displayed on a multifunctional screen (BMW) or as a standalone light (Nissan).
What to do if you see a DPF warning light.
When a DPF warning light shows on your dashboard, it is to tell you that ‘passive regeneration’ has failed, and so you need to actively regenerate the cars diesel particulate filter. Passive regeneration is the process that all diesel cars fitted with a DPF go through in order to prevent the build-up of soot.
Passive regeneration usually makes the car’s engine run more ‘rich’. This is where the car uses slightly more fuel than normal which raises the internal temperatures in the exhaust system burning the soot and turning into a fine ash which can pass through the DPF.
Active DPF regeneration usually occurs when the car is naturally running at a higher than average temperature. This is most likely achieved is when the car has been driving at over 40mph for longer than 15 minutes.
During both an active and passive regeneration, you may notice a few things such as a strange smell, a different idle noise coming from your engine or an increase in fuel consumption. These symptoms should all return to normal once the regeneration has completed and the DPF light will disappear.
What are the causes of a blocked DPF?
If you own a diesel vehicle, but mostly drive it on short low-speed commutes, or only around town the car cannot perform the regeneration process as the exhaust never reaches a high enough temperature. This will cause the engine to continue creating diesel soot adding to the build-up in the DPF eventually leading it to become blocked.
Other causes of DPF blockages can be due to an engine fault, such as too much oil being burnt off in the engine and blocking the catalytic converter and diesel particulate filter. Poor quality fuel can also cause DPF blockages as the impurities cannot be burnt off, finally build ups of carbon deposits can also contribute to a blocked DPF.
Can you ignore a DPF light?
You can ignore a DPF light, but it is not recommended. If you keep on driving the build-up of soot will eventually reach a point where there is too much back-pressure in the engine, where the exhaust gasses can no longer escape, causing the car to enter ‘limp mode’ in order to prevent any damages to the engine.
To fix a DPF light, even if the car is in limp mode, the most effective method is to take your car for a forced DPF regeneration or a more effective method of DPF cleaning. However, if the car has reached a level of damage to great to be fixed by these methods, a DPF replacement may be the only option available.