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; and c. Conformance criteria for the external test equipment.