The onboard diagnostic system (OBD) is almost standard on every modern vehicle. By exploiting the availability of wireless OBD dongles, vehicles can be assessed by the transportation authority and drivers to ensure compliance with emissions regulations. A vehicle’s OBD system can be remotely accessed by a fog node to retrieve a variety of the vehicle’s internal status and sensor readings. Such information can be shared with the transportation authority for registration renewal without the need for visiting emission stations. However, such automation comes at the risk of malicious intrusion into the OBD system by an attacker who aims to gain access to a vehicle’s internal network and control the vehicle. This article tackles this serious issue and proposes protocols for mutual authentication and securing the wireless connection between the OBD dongle, fog node, and authority. The robustness of the proposed protocols is verified using the Automated Validation of Internet Security Protocols and Applications (AVISPA) toolset.