The purpose of this Recommended Practice is to verify that vehicles and/or components are capable of communicating a required set of information, in accordance with the diagnostic messages specified in SAE J1939-73, to fulfill the off-board diagnostic tool interface requirements contained in the government regulations cited below. This document describes the tests, methods, and results for verifying diagnostic communications from an off board diagnostic tool (i.e., scan tool) to a vehicle and/or component. SAE members have generated this document to serve as a guide for testing vehicles for compliance with ARB and other requirements for emissions-related on-board diagnostic (OBD) functions for heavy duty engines used in medium and heavy duty vehicles. The development of HD OBD regulations by US EPA and California’s Air Resources Board (ARB) require that diagnostic message services are exercised to evaluate diagnostic communication standardization requirements on production vehicles. The user should reference the summary provided by SAE J1939-73 Tables 1 and 2 for OBD compliance support, and the discussion in SAE J1939-73 Appendix H for additional implementation concepts. The January 2016 version improved language that relies upon contextual technical details in referenced documents. An Engine Serial Number evaluation was added to 6.1 and 6.2. Wait times for fault erasure using DM3 and DM11 were increased to 5 seconds. The transition between part 7 and part 8 was improved to better assure that DM28 tests don’t experience a false positive outcome. Section A.6 was improved to separate evaluation of readiness bits provided by OBD modules from non-supported DM5 data provided by non-OBD modules. Data in Table A5B reflects the content of SAE J1939-DA of February 2015. Section A.10 was added to describe processing for PGNs that are only supported by some of the OBD modules under test. The February 2015 version of SAE J1939-84 replaced the test procedures in section 6 in order to implement a 2-operating cycle failure detection process for Production Vehicle Evaluation (l)(1) as requested by ARB. The tests also exercise diagnostic executive features such as three drive cycle accounting, freeze frame management and the general denominator in addition to the demonstration of interface function. Detailed criteria for some tests are described in a normative appendix, Appendix A, which was inserted before the output report examples that are now in Appendix B. The December 2008 publication of J1939-84 described a test process for EURO IV and EURO V engine emissions and diagnostics regulations, which is given in Section 7. The December 2010 version of the document added a test plan and procedure outline for ARB and US EPA HD OBD requirements with emphasis on 13 CCR 1971.1 (l)(1) Verification of Standardized Requirements, as Section 6. The June 2012 version added the observation of the MIL_On to MIL_Off transition for a single trip CCM fault and reformatted tables in Section 6 to improve ease of use.