Gasoline Particulate Filter — GPF

You already know about diesel particulate filters (DPF) that trap soot from diesel engines. A gasoline particulate filter — GPF — does the same thing for gasoline direct injection engines. GDI engines produce fine particulate matter (soot) because the fuel is injected directly into the cylinder and does not have as much time to fully mix with air before ignition. This soot is much finer than diesel soot — small enough to penetrate deep into your lungs. Emission regulations, especially in Europe, now require GPFs to capture it.

A GPF looks similar to a catalytic converter from the outside but has a different internal structure. It uses a wall-flow filter substrate — exhaust gas is forced through porous ceramic walls that trap particulate matter while allowing gas to pass through. As soot accumulates, the filter needs to regenerate — the ECM raises exhaust temperatures to burn off the trapped soot, converting it to CO2. This happens automatically during normal driving, similar to a diesel DPF regeneration but at lower temperatures because gasoline soot burns more easily than diesel soot.

GPFs are already standard on virtually all European-market gasoline vehicles from BMW, Mercedes-Benz, VW, Audi, and Hyundai/Kia. In the US market, adoption is increasing. Mercedes and BMW have GPFs on many US-market models. As EPA Tier 3 and CARB LEV III standards take effect, GPFs will become mandatory on US-market GDI vehicles as well. If you work on any European-brand vehicle made after 2018, assume it has a GPF.

GPF diagnosis is similar to DPF diagnosis. The vehicle has a differential pressure sensor measuring the pressure drop across the filter. The ECM monitors soot loading and initiates regeneration when needed. Common DTCs include high backpressure, regeneration failure, and differential pressure sensor faults. Short-trip driving (city driving that never lets the exhaust get hot enough) can prevent regeneration and cause the filter to clog — the same problem diesel vehicles have. If a GPF is plugged, the symptoms are reduced power, poor fuel economy, and potential engine warning lights. Backpressure testing with a gauge upstream of the GPF is the quickest way to verify the filter is flowing.