This paper talks about the methods of integrating diagnostics to existing fast charging standards such as CCS, GB/T and ChadeMO. Diagnostic methods and systems are commonly used and well-defined terms when associated with in-vehicle communication networks. It helps OEMs and vehicle manufacturers at several stages including development, pre-production and post-production. Commonly used standards are ISO-14229, ISO-14230 in conjunction with higher layer protocols such as ISO -15765. These standards define clear objectives in terms of services and methods.However, when it comes to fast chargers which are off-board chargers, diagnostics part is not yet standardized and is not much talked about. As a result, several manufactures/OEMs follow their own different strategies to deal with field failure detection and reporting. There are several problems why generic diagnostic standards applicable to in-vehicle communication networks does not apply directly on fast chargers. First problem being difference in communication methods. ChadeMo, GB/T follows CAN protocol with different baud rates and CCS follows PLC Communication. The paper defines the method where the dependence on communication is removed. Second problem is existing diagnostics standards have very fast data periodicity and with no on-fail strategies. However fast chargers have high voltage lines running in parallel with communication lines, so data loss is inevitable. The proposed embodiments define optimum timing requirements considering trade-off between speed and data loss. It also includes on-fail strategies even if data is being lost. Third problem is dependence on ignition cycles for most of the diagnostic services. For an off board charger, these services do not hold true. Proposed solution also takes care of defining cycles with respect to different services. Overall, the paper defines a systematic approach to integrate diagnostics in fast charging standards and eradicate the problems associated with it without intervening with existing fast charging standards.