DPF light on: regenerate the particulate filter or go to the garage?
Updated · Autofy
DPF light on: regenerate the particulate filter or go to the garage?
The DPF light means the particulate filter is too full of soot and couldn't clean itself. With no loss of power, the fix is often to let it regenerate: drive about twenty minutes at a steady speed on a fast road, following the procedure in your owner's manual. If the light stays on, flashes, or comes with a loss of power, the filter is too clogged or a sensor is at fault, and you need a diagnosis. Removing the DPF is illegal.
What the particulate filter does
The DPF traps fine soot particles produced by the engine so they don't leave through the exhaust. Fitted to every recent diesel, it's also found on recent direct-injection petrol engines as a gasoline particulate filter.
A filter inevitably fills up. To empty, it has to burn the soot: that's regeneration, which needs high exhaust temperatures reached only after several minutes of sustained driving.
Why the light comes on
When automatic regeneration fails several times, often because trips are too short to finish it, the filter loads beyond its threshold and the light comes on.
Other possible causes:
- A faulty differential pressure sensor that thinks the filter is full.
- An empty additive tank, on models that use one to help regeneration.
- An engine burning oil, whose ash doesn't burn off.
- A failing EGR valve or injector producing too much soot.
Triggering a regeneration
If the car isn't losing power:
- Check the owner's manual: many carmakers describe the exact procedure.
- Otherwise, drive about twenty minutes on a fast road at steady speed, in a gear that keeps the engine at sustained but not extreme revs.
- Avoid switching off during that time if you can: an interrupted regeneration starts over.
- Light goes out? Sorted. A regular fast-road run becomes a good habit.
When you need a garage
- The light stays on after a genuine regeneration attempt.
- It comes with a loss of power or the check engine light.
- It flashes, or the glow plug light flashes too.
A garage can run a forced regeneration with a scan tool, clean the filter, or replace it as a last resort. The longer you wait, the deeper the clogging.
What about removing the DPF?
Taking the filter out is illegal. The car no longer matches its type approval, fails emissions testing, and the driver risks a fine.
Keep track of your car's condition
Autofy keeps a record of every reported light and every repair, invoice photo included, so you can tell whether a problem keeps coming back. Every other light is in our dashboard warning lights guide.