The diagnostic port on a Class 8 truck can be in five different places depending on make, model and model year. This guide maps them all — the reference we built after identifying thousands of ports for customers.
Connector types: identify yours in 10 seconds
| Connector | Looks like | Era | Networks |
|---|---|---|---|
| 9-pin Deutsch Type 2 (green) | Round, 9 pins, green keying | 2016+ | J1939 @ 500k, CAN-FD |
| 9-pin Deutsch Type 1 (black) | Round, 9 pins, black keying | 2001–2016 | J1939 @ 250k, J1708 |
| 6-pin Deutsch | Round, 6 pins | 1988–2010 | J1708/J1587 |
| OBD-II 16-pin | Trapezoid, car-style | Medium-duty & vans | OBD-II, GMLAN, Ford MS-CAN |
| DoIP / Ethernet | RJ45 or OBD-to-Ethernet lead | 2025+ | Diagnostics over IP |
Port locations by make
| Make | Usual location | Connector |
|---|---|---|
| Freightliner Cascadia | Left of steering column, behind kick panel | 9-pin green |
| Kenworth T680/T880 | Center dash, below radio | 9-pin green (2014+), black earlier |
| Peterbilt 579/389 | Under dash, right of steering column | 9-pin green/black |
| Volvo VNL | Driver side, behind lower dash panel | 9-pin + OBD-style on some years |
| Mack Anthem/Pinnacle | Left dash, near fuse panel | 9-pin |
| International LT | Center console, behind cupholders on some trims | 9-pin green |
| Western Star 49X/57X | Left of column, Cascadia-style panel | 9-pin green |
| Hino / Isuzu LCF | Under driver seat or left dash | OBD-II style 16-pin |
When the port isn't enough
Some systems need direct-module access: trailer ABS at the ECU, CAT equipment at the machine harness, Volvo programming through dedicated leads. The cable finder flags these cases per vehicle; the off-highway page covers equipment-side connectors.
Frequently Asked Questions
Why does my truck have two diagnostic ports?
Common on newer trucks: one 9-pin for the J1939 backbone and an OBD-II-style port for body/infotainment systems. Volvo and International are frequent two-port platforms. Use the 9-pin for engine/ABS/aftertreatment.
The 9-pin port is dead — no power. What now?
Check the diagnostic-port fuse (usually labeled DLC or DIAG, 5–10A). Fleets sometimes pull it deliberately for anti-tamper; owner-operators sometimes find it blown by a cheap GPS tracker. Fuse map per model is in the cable finder notes.
Can I connect to J1708 trucks with a modern 9-pin cable?
Yes if the truck's 9-pin Type 1 carries J1708 on the correct pins (most pre-2016 trucks do) and your adapter supports J1708 (USB-Link 3, INLINE 8, DPA 5 all do).