I. Introduction
Connected fleets of vehicles have been extensively integrated into the Industrial Internet of Things (IoT) field globally [1], [2]. Through efficient collaboration, they achieve seamless data collection and extraction, thereby injecting new momentum into the optimization of operational models and the simplification of complex production processes [3]. In this context, vehicle malfunctions pose not only a significant threat to the safety of vehicle owners but also result in substantial labor costs for enterprises. Due to the exponential increase in vehicle-generated data and the significant resurgence of Artificial Intelligence (AI), data-driven Predictive Maintenance (PreM) has emerged as the most efficient solution to address the aforementioned issues [4]. Based on features extracted from state monitoring data, data-driven PreM methods can forecast the Remaining Useful Life (RUL) of components, estimating the time remaining before operational failure and guiding maintenance strategies [5]. The existing methods are primarily implemented by uploading data captured by on-board sensors to a central server for model training. However, transmitting these data wirelessly to the central server incurs significant wireless resource costs and communication delays, especially in the presence of a large number of moving vehicles. On the other hand, data captured by onboard sensors often includes sensitive privacy information, such as vehicle location, driver behavior, and onboard camera data. In recent years, there has been increasing interest in applying Federated Learning (FL) to the IoV [6], [7].