A Proposal to Re-architect Automotive OBD Freeze Frame Storage Requirements and the Associated Service-Oriented Freeze Frame Storage Algorithm Design 2018-01-0872

Automotive OBD freeze frame storage is mandated by regulations since the creation of OBD-II in 1994. The main purpose is to help service engineers to identify the cause of the associated fault. Although OBD regulations [1] have gone through multiple updates and major changes since 1994, the regulations requirements on freeze frame storage, however, remain almost the same. The flexibility to comply with the mandated requirements allows OEMs to come up with very different designs, and potentially would confuse the service engineers when repairing different powertrains and could compromise the main purpose of helping identify the root cause of faults. In 2015, GM fellows [2], together with SAE J1979 committee members, proposed a set of future requirements on the OBD freeze frame storage with the intention to standardize the requirements by mandating the rules what to store and when to store, the minimum number of frames, and the numbering of the frames. The proposal is better than the current requirements in terms of standardization and modernization, but it has several obvious shortcomings. For example, the minimum of four freeze frame storage will dramatically increase OEM’s costs and could potentially force OEMs to update their powertrain control units to have more storage capacity, and the downward compatibility with the current requirements is questionable. In addition, the prohibition of non-emission related faults in the freeze frames is not a service-friendly solution. Finally, the GM’s proposal gives no priority boarding for misfire or fuel system faults, which does not comply with the ARB CCR 1968.2 requirements. This paper proposes to re-architect the OBD freeze frame storage requirements with low cost to OEMs and downward compatibility to current requirements. In addition, a service-oriented freeze frame storage algorithm design is proposed based on the new requirements. This preliminary work offers OEMs an opportunity to extensively review theirs needs from service and designs and potentially will influence CARB to update the associated freeze frame requirements in the next version.