Short answer
DPF cleaning removes the soot and ash that regeneration cannot clear. The most thorough method takes the filter off the vehicle, bakes it to burn off soot and blows out the ash, then flow-tests it. On-vehicle chemical cleaning and fuel additives are cheaper but cannot remove ash.
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When DPF cleaning is needed
A healthy DPF keeps itself clear of soot through regeneration. Cleaning becomes necessary when regeneration can no longer keep up: the filter is loaded with ash after years of use, regeneration has been interrupted so often that soot has packed solid, or a fault has let too much soot reach the filter. Typical signs are a DPF warning light that keeps returning, frequent regenerations, loss of power or limp mode. See clogged DPF for the full list.
Find the cause first
A DPF rarely blocks for no reason. Faulty injectors, an EGR fault, a turbo leaking oil, a split pressure-sensor hose or a pattern of very short journeys can all overload the filter. A good DPF specialist diagnoses the vehicle before cleaning, because cleaning a filter without fixing the cause usually means it blocks again.
DPF cleaning methods compared
There are four broad approaches, and they are not equal.
- Fuel additives lower the temperature at which soot burns. They can help a lightly loaded filter regenerate but do nothing for ash. See DPF cleaners and additives.
- On-vehicle chemical cleaning sprays a cleaning fluid into the filter, usually through a sensor port, followed by a forced regeneration. It is quicker and cheaper, but most of the ash stays in the filter.
- Forced regeneration with a diagnostic tool burns soot while the vehicle is stationary. It is a regeneration, not a clean, and will not help an ash-loaded filter.
- Off-vehicle cleaning removes the DPF. Specialist DPF cleaning machines bake the filter to burn off soot, then use air pulses (or, on some systems, liquid) to clear the ash out of the channels. Flow testing before and after shows whether the clean worked.
What a proper clean includes
Whoever does the work, ask whether it includes diagnosis, a flow or back-pressure test before and after, a visual inspection of the ceramic faces for cracks or melting, new gaskets where required, and resetting the ECU’s soot and ash values after refitting. Without the reset, the ECU may still think the filter is full.
DPF cleaning near you
Cleaning quality varies, so compare what is included rather than price alone. Our guide to finding DPF cleaning near you lists the questions to ask, and the DPF cleaning cost guide explains what affects the price.
How DPF cleaning works
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Diagnose the vehicle
Read fault codes, check differential pressure readings, sensors and hoses, and look for the cause of the blockage.
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Remove the DPF
The filter is taken off the exhaust. Its condition and any cracks or melting are checked visually.
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Flow test before cleaning
A flow or back-pressure test records how restricted the filter is.
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Thermal clean and ash removal
The filter is heated in a controlled cycle to burn off soot, then ash is blown or flushed out of the channels.
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Flow test after cleaning
The result is compared with the first test to confirm flow has been restored.
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Refit and reset
The DPF is refitted with new gaskets if needed, and the ECU soot/ash adaptation values are reset with a diagnostic tool.
In this topic
DPF cleaning cost: what affects the price
What decides the cost of DPF cleaning, how it compares with regeneration and replacement, and how to compare quotes fairly.
DPF cleaning vs replacement: which do you need?
When a DPF can be cleaned, when it must be replaced, and how regeneration fits in. With a side-by-side comparison.