## 1 Introduction
The present methods are based on the examination of differential pressure sensor signals across DPFs. The measured pressure loss was dependent on several disturbance variables. Thus, differential pressure-based monitoring approaches for DPF would increase the difficulty of complying with future OBD legislation [15]. [PERSON], [PERSON] et al. demonstrated the EGS-PM-concept PM's and performance, as well as a novel concept for the OBD of DPFs that utilizes the EGS-PM [16]. The identification of the cause of damage by inspecting the damaged shape of the installed DPF with cracks or holes is an important factor in DPF development and powertrain evaluation [17]. The most effective experimental method involves the visualization of the cause of the DPF damage using X-rays. The ash and soot inside a homogeneous substrate can be measured using an X-ray scan when the X-ray contrast is sufficiently strong and edges can be identified in the image. However, large commercial vehicles with large and complex interior structures encounter difficulties even in this instance. Furthermore, ash and soot loadings frequently exhibit a gradually varying density distribution. This hinders their identification from the density pattern of the substrate [18]. [PERSON] et al. established the feasibility of using the widely available X-ray technology for a nondestructive measurement of ash and soot distribution [19]. [PERSON] et al. demonstrated the analytical capacity of the Tera-Hz-wave CT by measuring and comparing six samples with established requirements [20]. However, this technology has a disadvantage in that it is difficult to use in a manner that is rigorously regulated in accordance with radiation-related rules throughout the general vehicle inspection and management stage. However, most of the previous studies were focused on the main functions of DPFs, identification of the types of damage by X-ray technology, effects of DPF damage on the human body, and PM sensor-based OBD measurement. Therefore, it is necessary to systematically analyze their effects under the driving mode condition of a diesel-fueled vehicle in actual operation. To investigate this issue, it is crucial to evaluate whether additional examination is necessary, or to establish an X-ray site before performing a detailed X-ray examination of the DPF. In this study, the authors investigated the correlation between DPF failures and the OBD signal. This was aimed at detecting the type of damaged DPF. Figure 1 illustrates the detailed study process. These can be classified into the following four divisions:  
1. Classification of DPF failures with three samples  
In Korea, a state subsidy is provided when a DPF device is installed in an old diesel vehicle. Subsequently, when the vehicle is scrapped or the installed DPF device becomes obsolete, the supported DPF device is returned to the government, and the government manages it systematically. Therefore, in this study, DPF devices based on various types of  
Figure 1: Flowchart detailing this research process. damage were first selected using X-ray photoelectron devices for DPF devices that were old or damaged and retained in the country. 2. Vehicle operation on chassis dynamometer Three DPF samples with different types of damage were installed in the test vehicle. The KD-147 driving cycle was performed on a chassis dynamometer. 3. Analysis of OBD signal and PN data The OBD signal and PN data were measured from a test vehicle equipped with a damaged DPF device. The OBD data and PN emission characteristics of the DPF damage types were compared and analyzed. 4. Recommendation of algorithm to detect the type of damaged DPF Through these research divisions, the study was aimed at investigating the OBD signal and PN emission characteristics of various types of DPF-damage, and at presenting an algorithm for determining various types of DPF damage from vehicle OBD signals. This was because the OBD-based algorithm can rapidly determine whether a DPF is damaged, before precise identification by X-ray devices.