J1587 is an automotive diagnostic protocol standard developed by the Society of Automotive Engineers (SAE) for heavy-duty and most medium-duty vehicles built after 1985. SAE International (SAE is a professional organization for mobility engineering professionals in the Aerospace, Automotive, and commercial Vehicle industries The J1587 protocol uses different diagnostic connectors. Up to 1995, individual OEMs used their own connectors. From 1996 to 2001, the 6-pin Deutsch was standard. Beginning in 2001, most OEMs converted to the 9-pin Deutsch. Some OEMs still use the 6-pin Deutsch.
The pinout for the 9-pin connector is:
| PIN | SIGNAL |
| A | Ground |
| B | Unswitched +12 VOLTS |
| F | J1708Datalink (+) |
| G | J1708Datalink (-) |
The pinout for the 6-pin connector is:
| Pin | Signal |
| A | J1708Datalink (+) |
| B | J1708Datalink (-) |
| C | Unswitched +12 VOLTS |
| E | Ground |
J1708 makes up the datalink and physical layer that supports J1587. SAE J1708 is a standard used for Serial communications between ECUs on a heavy duty vehicle and also between a computer and the vehicle