This is a standard for high speed (Class C) communications between engine bay vehicle components in trucks, buses & similar heavy duty vehicles. The standard extends to the first five layers of the OSI 7 layer model (see below). The CANbus specification (data link layer) forms part of J1939; see below.

Published J1939 family documents are:

• J1939 Recommended practice for a serial control and communications vehicle network
• J1939/01 Recommended practice for control and communications network for on-highway equipment
• J1939/11 Physical layer - 250 kbit/s, twisted shielded pair
• J1939/13 Off-board diagnostic connector
• J1939/15 Reduced physical layer - 250 kbit/s, unshielded twisted pair
• J1939/21 Data link layer
• J1939/31 Network layer
• J1939/71 Vehicle application layer
• J1939/73 Application layer diagnostics
• J1939/74 Application - Configurable messaging
• J1939/75 Application layer - Generator sets and industrial
• J1939/81 Network management