DPF Cleaning

DPF cleaning sits between a forced regeneration and a new filter. When a diesel particulate filter is too blocked for a regeneration to clear but still sound, we clean it on the car, so it stays fitted and the car stays legal. We do this on most diesel makes and models.

• DPF warning light on the dash. Soot is building faster than it can burn off.

• Loss of power or limp mode. The engine protecting itself from the back pressure.

• Fuel use creeping up. Repeated regeneration attempts burning extra fuel.

• Engine management light. A stored fault from the filter or its pressure sensor.

A DPF clears itself by burning the soot off, but only once the filter reaches around 600°C. That needs a steady run on a dual carriageway or motorway, which a diesel used for school runs and town trips rarely gets. Switching the engine off part way through a regeneration has the same effect, and done often enough the filter blocks. A faulty sensor, engine oil that is not low SAPS or a nearly empty tank can each stop a regeneration from starting.

We read the soot load and back pressure before deciding anything. If a forced regeneration will clear it, we do that, since it costs less. If not, we clean it on the car. A filter that is cracked or packed with ash, which never burns off, has to be replaced, and we say so at the assessment rather than halfway through the job.

A cleaned DPF blocks again if the fault behind it is still there. We check the pressure sensor, the EGR valve and the injectors, because a fault upstream keeps sending extra soot into the filter. Where the driving pattern is the cause, we tell you that too.