A DPF warning light means your diesel particulate filter is filling up with soot faster than the car can burn it off. If you catch it early, a longer drive at a steady speed can sometimes clear it. If it stays on, it needs a garage, and a professional clean can often save you the cost of a new filter.
Here is what is going on, what you can try, and when to stop trying.
What the DPF does
The diesel particulate filter traps soot from the exhaust. Every so often the car burns that soot off in a process called regeneration, which needs the exhaust to get properly hot. That happens naturally on longer drives at a steady speed.
Why it blocks
- Mostly short, slow journeys, so the filter never gets hot enough to regenerate.
- Switching off partway through a regeneration, again and again.
- An underlying fault, such as a faulty sensor, injector or EGR valve, that makes the car produce too much soot.
- The wrong engine oil, or a service that is overdue.
What you can try when the light comes on
- Check the handbook for your car, as some have specific advice.
- Take a longer run on a faster road, typically 15 to 30 minutes at a steady 40mph or more, without stopping.
- Do not switch the engine off during it.
- If the light goes out, you are done. If it comes back, or other lights appear, stop trying and book it in.
A DPF light that is ignored can lead to loss of power, limp mode and a filter that cannot be recovered.
Cleaning or replacing
A new DPF can cost hundreds, even thousands, of pounds. Off-vehicle cleaning can restore a filter that is blocked but not damaged, for a fraction of that, which is why we invested in our own cleaning equipment.
We diagnose first, because if the cause of the blockage is a faulty part, cleaning alone will not fix it. See our DPF cleaning service.
How to keep it healthy
- Take a decent run every week or two if most of your driving is short.
- Use the oil your manufacturer specifies.
- Keep up with servicing.
- Do not ignore other warning lights, as they can be linked.
Quick answers
How do I clear a DPF warning light?
A longer drive at a steady speed can start a regeneration. If the light stays on, the filter needs professional attention.
Can I drive with the DPF light on?
For a short time, if the car drives normally. Do not ignore it for weeks, as it can end in limp mode or a ruined filter.
Is DPF cleaning worth it?
Often yes. It costs far less than a replacement, provided the filter is not physically damaged.
Does the DPF light fail an MOT?
It can, and a blocked DPF can cause an emissions fail. Have it looked at beforehand.