Learn about diesel particulate filters, regeneration, blocked filters and what government MOT guidance says.
A DPF is an emissions-control component on many diesel vehicles. It captures particulate matter from exhaust gases instead of allowing those particles straight into the air.
During normal operation trapped soot is periodically removed by regeneration, a high-temperature process. If regeneration is repeatedly interrupted or the vehicle has another fault, soot can accumulate and affect operation. Ash and other deposits may also accumulate over time.
A properly diagnosed, suitable filter may benefit from professional off-vehicle cleaning. This should be considered alongside the condition of the filter and the underlying cause of restriction. A damaged filter may require replacement.
UK government guidance explains that factory-fitted diesel particulate filters play a role in pollution control. Since February 2014, MOT checks include the presence of a DPF where one was fitted when the vehicle was built. A missing unit can result in an MOT failure.
The MOT inspection manual also lists missing, obviously modified or obviously defective manufacturer-fitted emissions equipment as a major defect.
Read the government guidance directly.
These sources provide general government information. They do not endorse a commercial cleaning service or guarantee particular test results.
