Diesel: DPF, AdBlue and glow plugs
Diesel particulate filter (DPF) warning light: what to do
The particulate filter warning light means the filter is heavily loaded with soot and has not been able to clean itself, which is typical of diesels used mainly for short trips. A drive at steady speed, as the handbook describes, is often enough for it to regenerate.
See a garage soonDiesel: DPF, AdBlue and glow plugs
Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Carefully, and only as far as the garage. Deal with it soon: follow the handbook's instructions to regenerate it. If the light does not go out, the car loses power or the engine light comes on, go to a garage: a badly blocked filter can be damaged or damage the turbo.
A careful, general answer: only someone who inspects the car can say whether it is safe to drive. When in doubt, stop somewhere safe and call for assistance.
Most likely causes
- Short trips: the exhaust never gets hot enough to burn off the soot.
- Interrupted regenerations: switching the engine off halfway through a regeneration leaves it unfinished.
- Differential pressure sensor or its pipes: false readings make it seem full or empty.
- Engine producing more soot: faults in the EGR, injectors, turbo or air-flow meter.
- Accumulated ash: at high mileage, ash that cannot be burnt fills the filter.
Listed from more to less common in general; on your car they may be different. A fault-code reading and a check at the garage confirm which one it is.
To understand it better: What is a particulate filter and how long does a regeneration take? What is EGR and what happens when it fails? What is AdBlue (DEF) and what happens if it runs out?
Car system: Exhaust and emissions
What you can check yourself
Check the handbook: many manufacturers ask for a few minutes at steady speed in a gear that keeps the engine at medium revs.
During a regeneration, avoid switching the engine off if the car indicates it.
Make sure you use the low-ash oil the manufacturer specifies.
If the light does not go out after the drive, do not insist: go to the garage.
Safe checks only: with the engine off and cold whenever you look under the hood, without taking anything apart and without touching hot or moving parts.
Related fault codes
- P2002Particulate filter (bank 1): efficiency below threshold
- P2463Particulate filter: restriction - soot accumulation (bank 1)
- P242FParticulate filter: restriction - ash accumulation (bank 1)
- P244AParticulate filter differential pressure (bank 1): too low
- P244BParticulate filter differential pressure (bank 1): too high
- P2452Particulate filter pressure sensor A, circuit: malfunction
- P2459Particulate filter regeneration frequency (bank 1): malfunction
Generic codes that often come with this symptom. Seeing one does not confirm the cause: it is where the diagnosis starts.
How the ECO-LITE helps diagnose it
Plugged into the OBD socket, the ECO-LITE reads the fault codes of the control units that answer, with the freeze-frame data captured when the fault happened, and shows live data on your phone or computer. With your permission, your garage can see them remotely before you bring the car in.
What to look at here: estimated soot load and filter differential pressure, exhaust temperatures and regeneration status, depending on what the car reports.
Frequently asked questions
How long do I have to drive for it to clean?
Your car's handbook says; it is usually a drive of some minutes at steady speed. If the light does not go out, have it checked.
Can the filter be cleaned without replacing it?
Often yes: with a forced regeneration from a diagnostic tool or a workshop clean. It depends on how much ash it holds.
Is it legal to remove the particulate filter?
No: disabling it is illegal in the EU, the car fails its inspection (such as the MOT) and it emits harmful particles.
Keep reading
- Exhaust and emissions: how they work and what fails
- Particulate filter regenerating too often: causes
- Car loses power: what limp mode is
- Black smoke from the exhaust: causes and what to do
- Car symptoms: what they mean and what to do
- Check engine light on: what to do
- How to read and clear your car's fault codes
- OBD fault codes: what each one means