Emissions Control Systems

Diesel Particulate Filter Purpose

The Diesel Particulate Filter (DPF) captures and burns soot from exhaust. Modern diesel engines produce fine particulate matter (PM) during combustion - tiny carbon particles that are harmful to human health and the environment. The DPF traps these particles in a honeycomb ceramic substrate, preventing them from entering the atmosphere.

Regeneration Process

As the DPF collects soot, back pressure increases and the filter must be cleaned. This cleaning process is called regeneration - burning accumulated soot at high temperature. There are three types of regeneration:

Passive regeneration occurs naturally during highway driving when exhaust temperatures are high enough to burn soot without intervention. Active regeneration is initiated by the ECM when soot loading reaches a threshold. The ECM injects additional fuel (either late injection or a dosing valve) to raise exhaust temperature to 1100-1200 F, burning the accumulated soot.

Forced (stationary) regeneration is performed by the technician using a diagnostic tool when active regeneration has failed or been interrupted repeatedly.

The DPF captures and burns soot from diesel exhaust. Regeneration is the process of burning accumulated soot at high temperature. The exam will test your understanding of all three types - passive (natural), active (ECM-initiated), and forced (technician-initiated).