DPF light on? What it means and what to do
The short answer
The DPF light means the diesel particulate filter in your exhaust is getting clogged with soot and needs to burn it off. If it's a steady light on its own, a longer steady drive at motorway speed will often let the filter clean itself and clear the light. If the light is flashing, other warnings have joined it, or the car has dropped into limp mode, stop driving hard and get it checked before the blockage gets worse.
The DPF is a filter that traps the soot from a diesel engine so it doesn't come out of the exhaust. Every so often the car burns that soot off in a process called regeneration. The warning light is the car telling you the soot has built up and a regen either needs to happen or has failed to finish.
Common causes and what they mean
A few things could be behind it. Here's what each usually points to, and how serious it is.
Too many short journeys
Lots of short, stop-start trips never let the exhaust get hot enough to regenerate. The soot builds up with nothing burning it off, which is the most common reason the light comes on.
Interrupted regeneration
If you switch the engine off partway through a regen, or never drive far enough for one to finish, the cycle never completes and the filter stays full.
Sensor fault
The car works out how blocked the filter is from pressure and temperature sensors. A faulty sensor can trigger the light or stop a regen starting even when the filter is fine.
EGR valve problem
A sticking or clogged EGR valve upsets the engine and makes it produce more soot than normal, which loads the DPF up faster. See our EGR valve cleaning if that's the cause.
A genuinely blocked filter
If the light has been ignored for a while the filter can clog to the point it won't regenerate on a drive at all, and it needs a forced regen or a proper clean.
Can I still drive with the DPF light on?
A steady DPF light on its own is usually the car asking for a longer run, so a 20 to 30 minute drive at a steady 50 to 60mph in a lower gear will often trigger a regen and clear it. If that doesn't clear it, or the light is flashing, or other warning lights come on, or the car goes into limp mode with the power cut back, stop driving it hard and get it checked. Carrying on with a badly blocked filter can force a garage regen or a new DPF, which is a far bigger bill than sorting it early.
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