On-board diagnostics (OBD) is a term referring to a vehicle's self-diagnostic and reporting capability. It is a system originally designed to reduce emissions by monitoring the performance of major emission related components. There are two kinds of on-board diagnostic systems: OBD-I and OBD-II. In India OBD I was implemented from April 2010 for BS IV vehicles. OBD II was implemented from April 2013 for BS IV vehicles. Apart from the comprehensive component monitors, OBD II system also has noncontinuous monitors like Catalyst monitoring, Lambda monitoring, and other after treatment system monitors. For OBD II verification and Validation, it is required to test all the sensors and actuators that are present in the engine, for all possible failures. From an emissions point of view there are lists of critical failures that are caused due to malfunction of sensors and actuators. Carrying out the full matrix failure testing on the running engine could be tedious, unsafe and time consuming. Hardware in Loop (HIL) can be the effective solution testing and full matrix OBD validation. Apart from the major categories of vehicle, OBD regulations are more stringent for commercial vehicles as have direct torque limitation in case of failure of emission related component. A commercial vehicle EMS was selected for OBD full matrix V&V in HIL. This paper talks about the methodologies authors have implemented during the course of OBD V&V. The results so obtained and performance evaluation is presented in respective sections.