This part of ISO 15031 provides guidance on the usage of terms, definitions, abbreviations and acronyms used in emissions-related diagnostics, with respect to the communication between road vehicles and external equipment used in that field. It also specifies a procedure for constructing new terms. As it gives recommended usage of diagnostic terms applicable to electrical/electronic systems, it also makes reference to related mechanical terms, definitions, abbreviations and acronyms. This part of ISO 15031 is applicable to all light-duty gasoline and diesel passenger vehicles and trucks, and to heavy-duty gasoline vehicles. Specific applications of this document include diagnostic, service and repair manuals, bulletins and updates, training manuals, repair databases, underhood emission labels and emission certification applications. The introduction of a term, abbreviation or acronym not covered by this part of ISO 15031 is not prohibited. This part of ISO 15031 is intended to help industry provide standard terms, definitions, abbreviations and acronyms with a view to establishing a common terminology for diagnostic tools and publications.