In preparation for the 2019 Q3 modifications to the reporting of System and Component IDs during missing data periods, EPA has posted a white paper which details the changes. This document includes reporting guidance for different system types and the new MODC codes.
Additionally, an updated draft subset of the ECMPS Emissions Reporting Instructions has been posted for review. The changes, in Redline Strikeout format, affect Sections 2.5.1 Monitored Hourly Value Data and 2.5.2 Derived Hourly Value Data. The updated document can be found here. Once finalized, these edits will be incorporated into the 2019 Q3 version of the ECMPS Emissions Reporting instructions. The changes will also be included in the 2019 Q3 ECMPS software release.
New check messages returned as a result of these changes will be informational at first. The severity will be increased no sooner than 2020 Q1.