Diesel: DPF, AdBlue and glow plugs
Particulate filter regenerating too often: causes
A diesel with a particulate filter burns off the soot from time to time: that is regeneration. If it happens very often, the engine is producing more soot than normal, the sensor is misreading or the trips do not let it finish, and that raises consumption and can dilute the oil.
Check without hurryDiesel: DPF, AdBlue and glow plugs
Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Usually not urgent, but do not ignore it. It is not urgent, but it is not normal either: have it checked before it ends in a blocked filter or the DPF light coming on.
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: regenerations are interrupted and repeated over and over.
- Differential pressure sensor: a falsely high reading asks for regeneration when it is not needed.
- EGR or air-flow meter: a sootier mixture fills the filter sooner.
- Injectors: poor spray creates more particles.
- Ash: at high mileage the filter has less usable space.
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? Why is stop-start not working? What is EGR and what happens when it fails?
Car system: Exhaust and emissions
What you can check yourself
Signs of regeneration: the fan running after you switch off, a higher idle, a hot smell or stop-start disabled.
Check the oil level: if it rises, it may be diluted with diesel from the regenerations.
If you mostly make short trips, add a longer one at steady speed from time to time.
Ask for the soot load and the distance since the last regeneration to be read.
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
- P2459Particulate filter regeneration frequency (bank 1): malfunction
- P2458Particulate filter regeneration duration (bank 1): malfunction
- P2463Particulate filter: restriction - soot accumulation (bank 1)
- P2452Particulate filter pressure sensor A, circuit: malfunction
- P0401EGR A flow: insufficient flow detected
- P2002Particulate filter (bank 1): efficiency below threshold
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, distance since the last regeneration, differential pressure and exhaust temperatures, depending on the car.
Frequently asked questions
How do I know the car is regenerating?
Many cars do not show it. Clues: the fan running after you switch off, a higher idle, a hot smell or stop-start not working.
Why does the oil level rise?
Some regenerations let a little diesel into the oil; if the level rises, change it sooner and find out why it regenerates so much.
Does it matter if I switch off during a regeneration?
Once is not serious; if it happens every time, the filter fills up and ends up lighting the warning.
Keep reading
- Exhaust and emissions: how they work and what fails
- Diesel particulate filter (DPF) warning light: what to do
- Car uses more fuel than normal: causes and what to check
- 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