Change Car Particulate Filter (DPF)
The particulate filter (DPF on diesel, GPF on direct-injection petrol) traps the soot particles given off by the engine. A clogged DPF reduces engine power and can lead to a complete breakdown. Its regeneration is normally automatic, but is not always possible with heavy urban use.
How does the particulate filter work?
At idle and under light load, the particles are trapped in the ceramic filter. When driving under high load, the exhaust gases reach 550 to 600 °C and burn off the accumulated particles: this is passive regeneration. If the conditions are not met, the ECU triggers an active regeneration by enriching the injection.
What to do if the DPF light comes on?
As soon as the warning light comes on, drive for around fifteen kilometres at over 60 km/h at sustained revs until the light goes out. If the light stays on, a specialist will need to carry out a forced regeneration with a diagnostic tool.
Replacing the particulate filter
Variable difficulty
If the DPF is under the vehicle, replacement is quick (about 1 hour). If it sits between the engine and the bulkhead, the engine subframe has to be dropped (about 4 hours).
Diagnostic tool essential
After fitting, you must reset the "ash quantity" figure stored by the engine ECU. Without this step, the system will manage regeneration incorrectly.
Identify the cause
A DPF never clogs without a reason. Check the engine oil quality, the condition of the injectors and the EGR valve before replacing. Otherwise the new filter will be damaged prematurely.
Price
Between £250 and £1,200 depending on the vehicle. Average garage price: around £600 for the part, excluding labour.
DPF regeneration
Passive regeneration
Happens automatically when driving on a main road or motorway, when the exhaust temperature is high enough (around 600 °C). This is the normal mode of operation.
Active regeneration
Triggered by the engine ECU when clogging reaches a critical threshold. Post-injections of fuel raise the exhaust temperature. The process lasts 10 to 20 minutes and the engine may run a little differently.
Forced regeneration
Carried out in a workshop with a diagnostic tool when the automatic regenerations have failed. If this method fails too, the DPF must be replaced.
