SAE J1298 covers the recommended diagnotic port sizes for use in measuring hydraulic fluid temperature, pressure, flow, and for obtaining fluid samples. See SAE J1502 for the detailed coupling specifications.
Reviewed the document and updated it. Reference to SAE J2244-2 are removed because that document is being withdrawn and replaced by ISO 6149-2. All references to the year of publication of ISO documents are removed as the users are urged to used the latest edition of the document.