A new revision of J2191 has been published by SAE International. J2191 applies to “Recommended Practice for Identification of Standardized Truck and Tractor Electrical Circuits.” The new revision is available for purchase on the SAE website.
“This SAE document defines a recommended practice for implementing circuit identification for electrical power and signal distribution systems of the Class 8 trucks and tractors. This document provides a description of a supplemental circuit identifier that shall be utilized in conjunction with the original equipment manufacturer’s primary circuit identification as used in wire harnesses but does not include electrical or electronic devices which have pigtails.”
*Description from SAE website