If you drive a modern diesel, there’s a good chance you’ll see the DPF warning light at some point. Here’s what it means and what to do about it.
What is a DPF?
A diesel particulate filter sits in the exhaust and traps the soot a diesel engine produces. Over time the filter fills up, so the vehicle periodically raises the exhaust temperature to burn the soot off. This is called regeneration.
Why the light comes on
Regeneration needs the exhaust to stay hot for a while — typically during a steady drive at higher engine speeds. Short journeys, stop-start traffic and lots of low-speed driving can stop it completing, so soot keeps building up until the vehicle warns you.
Underlying faults can also cause it: a faulty pressure sensor, EGR valve problems, injector issues or the wrong grade of engine oil can all make soot build up faster than it can be burned off.
What to do when the light comes on
- Check the handbook. Many manufacturers recommend a specific drive to help the filter regenerate — often a period of steady driving on a faster road, where it’s safe and legal.
- Watch for other warnings. If the engine management light is also on, or the vehicle has gone into reduced power, get it checked rather than trying to drive it clear.
- Don’t ignore it. Continuing to drive with a heavily blocked filter can lead to more expensive problems.
- Get it diagnosed. A diagnostic check shows the soot load and the pressure readings, and can reveal whether a fault is behind the blockage.
Cleaning versus removal
You may see DPF “removal” advertised. Removing or tampering with a DPF on a road vehicle is illegal in the UK and causes an MOT failure. The right fix is to find the cause, clean the filter and get regeneration working properly again.
Preventing it happening again
- Give the vehicle a longer, steady run regularly if most of your driving is short trips.
- Use the engine oil specification the manufacturer recommends.
- Don’t ignore other warning lights — they can be linked.
This article is general guidance. Every vehicle is different — for advice on yours, call 07714 508420.