Sixteen pins, four that matter for DoIP — and the reason cheap cables with the wrong pinout fail intermittently.
The OBD2 (SAE J1962) connector predates DoIP by two decades — the Ethernet pins were assigned later. Here's the full map with the DoIP-relevant pins highlighted in context.
| Pin | Assignment | DoIP Relevance |
|---|---|---|
| 2 | Bus+ (SAE J1850) | Legacy |
| 4 | Chassis ground | ✓ required for ENET adapters |
| 5 | Signal ground | ✓ required |
| 6 / 14 | CAN-H / CAN-L (ISO 15765) | Classic OBD2 diagnostics |
| 7 / 15 | K-Line / L-Line (ISO 9141) | Legacy |
| 8 | DoIP activation line | ✓ wakes the Ethernet gateway |
| 10 | Bus− (SAE J1850) | Legacy |
| 12 / 13 | Ethernet TX+ / TX− (100BASE-TX) | ✓ the DoIP data pair |
| 16 | Battery +12V | ✓ powers the adapter |
DoIP runs on 100BASE-TX — a single twisted pair on pins 12/13 carries 100 Mbit/s in both directions. Pins 4/5 ground the link, pin 16 powers the adapter, and pin 8 (the activation line) tells the vehicle gateway to bring its Ethernet PHY up. When you plug in an ENET cable and get a 169.254.x.x address, this is the exact hardware conversation that just succeeded.
This is also why pinout QA is not marketing fluff: swapped 12/13 or a missing activation line produces the classic 'cable connects sometimes, drops during coding' failure. Every adapter we ship is continuity-tested against this map — the failure modes it prevents are documented in the troubleshooting guide.