If you drive a diesel car registered after around 2009, it is fitted with a Diesel Particulate Filter (DPF). When the DPF warning light comes on, it needs attention sooner rather than later.
What is a DPF
A DPF is a filter in the exhaust system that traps soot particles from the combustion process, preventing them from being released into the atmosphere. Over time the filter fills with soot and needs to be cleaned out. This cleaning process is called regeneration.
How regeneration works
The car attempts to regenerate the DPF automatically by raising exhaust temperatures high enough to burn off the accumulated soot. This normally happens during sustained motorway or dual carriageway driving at speed. Short urban journeys and stop-start driving do not generate enough heat for regeneration to complete, which is why city-based diesel drivers are most likely to see the DPF light.
What the warning light means
The DPF light (usually an amber light showing a filter shape with dots, or sometimes described in a dashboard message) indicates the filter is becoming full and a regeneration cycle is needed. At this stage, the fix is usually simple: take the car for a 15 to 20 minute motorway or dual carriageway drive at a steady speed above 50 mph. The regeneration should complete and the light should go out.
When the light stays on or turns red
If the light remains on after a long motorway drive, or if it has been ignored for a while and turned red or amber along with a power reduction, the DPF may be too blocked for passive regeneration to work. At this point the car needs a forced regeneration carried out by a garage using diagnostic equipment, or in severe cases a DPF clean or replacement.
Ignoring a DPF warning until the car goes into limp mode or the filter cracks is a costly mistake. If you are not sure what your DPF light means or the light has been on for more than a day or two, call Steins Garage on 0131 554 3423 or get in touch here.