SAE J1978_200204

This SAE Recommended Practice supersedes SAE J1978 FEB1998, and is technically equivalent to ISO/DIS 15031-4:December 14, 2001. This document is intended to satisfy the requirements of an OBD scan tool as required by U.S. On-Board Diagnostic (OBD) regulations. The document specifies: a A means of establishing communications between an OBD-equipped vehicle and external test equipment, b A set of diagnostic services to be provided by the external test equipment in order to exercise the services defined in SAE J1979, c Conformance criteria for the external test equipment. ISO 15031-4 was created to be referenced in OBD regulations outside of the United States, and contains the same technical content as the previous version of SAE J1978 with the following additions: a Provisions for ISO 15765-4 (CAN) as a diagnostic serial data link (only 500 Kbps is allowed in U.S. regulations). b Allowance for 24 V DC connector as defined in ISO 15031-3 (not allowed in U.S. regulations).. This document was issued to include the same technical content, in the same order, and with the same section references as the ISO document, but includes exceptions required by proposed U.S. regulations. NOTE— To maintain equivalency of the documents, a comma is used as a decimal marker for numeric values in this document.