Malfunctions in Selected Emissions-Related Components of Euro 4 Passenger Cars: Emissions Increase and OBD System Response

As new passenger cars are constantly getting cleaner, their contribution to air pollution is in large part defined by the in-use emissions degradation. In this respect, malfunctions in emissions-related components may play an important role to the contribution of passenger cars in air pollution. This paper assesses the impact of malfunctions of selected emissions related components to the pollutant emissions and evaluates the response of the OBD system to these malfunctions, under legislated and non-legislated driving cycles. The emissions-related components subjected to malfunctions are, for gasoline fuelled cars oxygen sensor and catalytic converter, and for diesel cars Exhaust Gas Recirculation system (EGR) and diesel Particulate Filter (DPF). For gasoline cars, the results show that total malfunctions of the above components result in up to two orders of magnitude increase in pollutant emissions. For diesel cars, total malfunctions in the EGR system lead to 2–6 times increase of NO_x emissions. Removal of the DPF leads to 20 times increase of PM emissions, in terms of PM mass, and up to 3 orders of magnitude increase in terms of particle number. The OBD system detected these malfunctions accurately in the legislated driving cycle. However, the ability of the OBD system to detect the malfunctions in the non-legislated driving cycles presented a high variability between the different cars tested.