During regeneration the engine burns the soot collected in the particulate filter: it usually lasts 10-20 minutes and must not be interrupted by switching the engine off. Repeated interruptions are the leading cause of a clogged DPF.
What DPF regeneration is
The particulate filter traps soot from the exhaust gases. When it fills, the control unit raises exhaust temperature (above 550-600 °C) with a post-injection of fuel and burns it. It is a normal cycle, repeating every few hundred kilometres depending on use: it is not a fault.
- Passive: on the open road exhaust temperature is enough to burn the soot unnoticed
- Active: the control unit steps in with post-injection when the filter load passes a threshold; this is the one you notice
- Forced (static): started by a technician with the diagnostic tool when the car cannot manage by itself
How to recognise a regeneration
- Higher idle and cooling fan always on
- Acrid smell and light white smoke from the exhaust, sometimes a hiss or hum
- Higher instantaneous consumption and start-stop disabled
- On some cars a dedicated message appears or the DPF light flashes or stays on
- The engine feels slightly sluggish until the cycle ends
How long it lasts
A cycle lasts typically 10-20 minutes of driving. The interval between regenerations depends on use: from a few hundred kilometres for city driving to over 1,000 on open roads. If the frequency rises noticeably, it is a sign: the filter, or something upstream (EGR, injection, sensors), is working worse than normal.
What to do
- If you can, keep driving 15-20 minutes at a steady speed, preferably above 2,000 rpm
- Avoid switching the engine off before the cycle has ended
- Respect oil change intervals: fuel mixes with the oil during regenerations
- Use the "low SAPS" oil specified by the manufacturer: the wrong oil leaves more ash in the filter
What not to do
- Do not repeatedly switch off during the cycle: soot builds up and the filter clogs
- Do not ignore a steady DPF light: from then on the car often cannot do it alone
- Do not rely on "miracle" additives instead of maintenance
- Do not drive long with warning lights on: you may end up in limp mode
How much does it cost to fix?
| Work | Indicative cost |
|---|---|
| Forced regeneration | €60-150 |
| Professional cleaning | €150-350 |
Figures are indicative market ranges, useful for orientation: the real cost depends on model, engine, parts chosen and labour hours. For an exact quote we need the vehicle registration number.
How MasterTuning helps
We read the real values of the control unit, not just the code: that is the difference between finding the faulty component and replacing parts by trial and error. After the repair we clear the error and check that it does not come back. Find the nearest centre or contact us.
Does your DPF clog often? Book a diagnosis at the nearest MasterTuning centre.
Frequently asked questions
How long does DPF regeneration last?
Usually 10-20 minutes of driving. If interrupted, the car will try again on the next cycle; continuous interruptions lead to a clogged filter.
What happens if I switch the engine off during regeneration?
The cycle stops and soot stays in the filter. Repeated often, the DPF clogs until you lose power and the light stays on.
How do I know the regeneration has finished?
Fan switches off, idle returns to normal, white smoke and acrid smell disappear, start-stop works again.
Can I do a regeneration while stationary?
Static regeneration must be done in a workshop with the diagnostic tool, monitoring temperatures and filter load.
