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This SAE Recommended Practice 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, under-hood emission labels, and emission certification applications. This document focuses on diagnostic terms applicable to electrical/electronic systems, and therefore also contains related mechanical terms, definitions, abbreviations, and acronyms. Even though the use and appropriate updating of this document is strongly encouraged, nothing in this document should be construed as prohibiting the introduction of a term, abbreviation, or acronym not covered by this document. Certain terms have already been in common use and are readily understood by manufacturers and technicians, but do not follow the methodology of this document.

SAE J1978 defines the requirements of the OBD II scan tool. SAE J2201 defines the minimum requirements of the vehicle communications interface for the SAE J1978 OBD II scan tool. This interface connects the SAE J1962 test equipment connector to the hardware/software of the SAE J1978 OBD II scan tool that will use this interface to communicate with vehicles for the purpose of accessing required OBD II functions. Included in this SAE Recommended Practice are several definitions relating to the interface, and interface functionality evaluation. Appendix A - Examples include several example interface circuit implementations, which are believed to meet the requirements of this document and of SAE J1978. These examples are NOT requirements of this document. They are provided to assist circuit designers in developing interface circuits. Appendix B - Supporting Documents includes a list of supporting documents for the examples shown in Appendix A.

The SAE J1962 diagnostic connector consists of two mating connectors, the vehicle connector (see Figure 1) and the test equipment connector (see Figure 2). This document: a Defines the functional requirements for the vehicle connector. These functional requirements are separated into three principal areas: connector location/access, connector design, and connector terminal assignments. b Defines the functional requirements for the test equipment connector. These functional requirements are separated into two principal areas: connector design and connector terminal assignments.

This SAE Recommended Practice establishes a uniform practice for protecting vehicle modules from "unauthorized" intrusion through a vehicle diagnostic data communication link. The security system represents a recommendation for motor vehicle manufacturers and provides flexibility for them to tailor their system to their specific needs. The vehicle modules addressed are those that are capable of having solid-state memory contents altered external to the electronic module through a diagnostic data communication link. Improper memory content alteration could potentially damage the electronics or other vehicle modules; risk the vehicle compliance to government legislated requirements; or risk the vehicle manufacturer's security interests. This document is intended to meet the "tampering protection" provisions of California Air Resources Board OBD II regulations and does not imply that other security measures are not required nor possible.

This document is applicable to all light duty gasoline and diesel vehicles (LDV), light duty gasoline and diesel trucks (LDT), and heavy duty gasoline vehicles (HDGV). Specific applications of this document include service and repair manuals, training manuals, repair data bases, under-hood emission labels, and emission certification applications. Even though the use and appropriate updating of this document and its companion documents is strongly encouraged, nothing in these documents should be construed as prohibiting the introduction of a term or acronym not covered by these documents.