This article proposes a diesel oxidation catalyst diagnostics strategy based on the exothermic process generated by exhaust gas species oxidation in the catalyst. The diagnostics strategy is designed to be applied on-board and respecting real-time electronic control unit computational limitations. Diagnostics purposes are fulfilled by means of the comparison of the passive model temperature, which represents the outlet temperature of a non-impregnated diesel oxidation catalyst, and the measurement provided by the on-board catalyst-out temperature sensor. Thus, the presented diagnostics strategy uses only two production grade temperature sensors and the measurements of air and fuel mass flows from the electronic control unit. Passive diagnostics is based on the oxidation of engine-raw emissions, whilst active diagnostics is based on the oxidation of requested post injected fuel. Post-injection strategy is also discussed for active diagnosis. Then, the diagnostics strategy is able to discern whether the diesel oxidation catalyst is able to oxidise or not. (C) 2016 Elsevier Ltd. All rights reserved.

On-board diagnosis of the after-treatment system is forced by regulation; with diagnosis limits approaching certification values, a tight surveillance of the after-treatment performance is to be done. This paper presents a simple model for a diesel oxidation catalyst, representing both the thermal and chemical behaviour of the system. In addition to the model description, the paper provides hints on the model fitting process and illustrates its performance in several driving conditions. Despite its simplicity, the model allows a proper description of the exhaust temperature variation, allowing the implementation of several model based diagnostic techniques.