## 1 **Introduction**  
### **1.1** **Motivation**  
Lower emission standards and new test protocols such as those for the Worldwide harmonized Light vehicles Test Procedure (WLTP) and Real Driving Emissions (RDE) have increased the challenges for Original Equipment Manufacturers (OEMs) and suppliers to develop advanced and more efficient exhaust gas aftertreatment systems [1; 2; 3]. With Euro 7 legislation under discussion, these challenges will continue to increase [4; 5].  
Considering EU6d, additional hardware and their respective control functionalities, such as gasoline particulate filters (GPF), already have been introduced [6; 7; 8; 9; 10; 11; 12]. Additionally, advanced methods are being developed to ensure emission robustness and compliance up to the full useful life of the exhaust aftertreatment system (EATS) [6; 13]. State of the art strategies ensuring RDE compliance have also been developed to cope with the broad and comprehensive test matrix required to effectively cover all possible RDEscenarios [14; 15; 16; 17]. Hence, the ultimate goal is the zero impact emission vehicle, such as investigated by [PERSON] et al. and [PERSON] et al. [1; 18].  
To comply with Euro 7 emission targets, both internal and external engine measures are being considered. For example, second-generation GPFs with higher filtration efficiencies as well as engine operation with a stoichiometric air-fuel ratio (\(\lambda=1\)) in the entire engine map are two examples of modern measures being used [19; 20; 21]. Also, the installation of additional components into the exhaust aftertreatment system is an option. For example, electrically heated catalysts, hydrocarbon (HC) absorbers and secondary air systems are currently further developed, which require new operating strategies as well [22; 23].  
The technologies associated with advanced aftertreatment systems, as well as the introduction of hybrid powertrain technologies, translate into a substantially larger number of components and control systems to be diagnosed under on-board diagnosis (OBD) legislation. On one hand, the number of diagnosis concepts are becoming more and more comprehensive; on the other hand, the calibration and validation efforts are increasing notably with increased and more elaborate test scopes. With the current conventional calibration methodology, this necessitates an increased need for additional prototype vehicles and chassis dynamometer time.  
In the context of Road-to-Rig-to-Desktop approaches [24; 25; 26], this paper presents a feasibility study for transferring OBD-related calibration and validation tasks from the vehicle to a Hardware-in-the-Loop (HiL) platform. The next subchapter describes the methodology and the requirements to enable HiL-based OBD engineering tasks during powertrain development. The second chapter introduces the reference vehicle, the main engine and the exhaust aftertreatment specifications. It also introduces the specifications of the closed-loop HiL platform, including a brief introduction of the real-time powertrain models. To demonstrate the performance of the HiL platform, the subsequent chapter discusses the case example of the active diagnosis for monitoring the status of the three-way catalyst (TWC) and the oxygen sensors in the exhaust gas aftertreatment system. Finally, the presented approach is discussed with regard to its advantages in terms of project time and required resources.