Every common CAN bus connector in one place: verified pinouts you can explore pin by pin, wiring diagrams between any two connectors, and the checks that find most CAN faults — termination, bus length and stub length.
Seven connectors cover almost every CAN bus you will meet: the J1939 9-pin diagnostic port on heavy trucks (black Type I and green Type II), OBD-II in cars and light trucks, the 3-pin Deutsch DT on J1939 backbones, and DB9, M12 and RJ45 on interfaces and industrial gear. Each page shows the face drawing, an interactive pin table, OEM variants, history and a free pinout diagram to download.
The black heavy-duty diagnostic port: CAN on C/D, battery on A/B, J1708 on F/G.
The 500 kbit/s-capable 9-pin: same letters, keyed so old 250 kbit/s tools can't plug in.
The 16-pin port in every car: CAN on 6/14, ground 4/5, battery on 16.
The CiA layout on almost every PC CAN interface: 7 High, 2 Low, 3 ground.
The triangular plug on truck and machine CAN backbones and terminators.
The sealed, threaded connector of CANopen, DeviceNet and NMEA 2000.
CAN over patch cable: CiA puts the pair on 1/2 — but vendors differ.
Answer two or three questions about where it is and what it looks like.
Where CAN High, CAN Low, ground and power sit on each connector — the four pins that matter when you build an adapter.
| Connector | Standard | Pins | CAN High | CAN Low | Ground | Power | Shield |
|---|---|---|---|---|---|---|---|
| J1939 9-pin (Type I) | SAE J1939-13 | 9 | C | D | A | B | ✓ |
| J1939 9-pin Type II (green) | SAE J1939-13 Type II | 9 | C | D | A | B | ✓ |
| OBD-II (J1962) | SAE J1962 / ISO 15031-3 | 16 | 6 | 14 | 4, 5 | 16 | — |
| DB9 / D-Sub 9 (CiA) | CiA 303-1 / CiA 106 | 9 | 7 | 2 | 3, 6 | 9 | ✓ |
| 3-pin Deutsch DT | SAE J1939-11 / J1939-15 | 3 | A | B | — | — | ✓ |
| M12 5-pin A-coded | CiA 303-1 / DeviceNet / NMEA 2000 | 5 | 4 | 5 | 3 | 2 | ✓ |
| RJ45 / 8P8C (CiA) | CiA 303-1 / CiA 106 | 8 | 1 | 2 | 3, 7 | 8 | ✓ |
Choose any two connectors to get a pin-to-pin wiring diagram, with wire colours, which pins to leave unconnected, and the power and termination warnings that matter. Hover a wire to trace it.
Pick two connectors to draw the wiring. (Needs JavaScript.)
Quick checks for the faults we see most: wrong termination, a bus too long for its bit rate, and stubs that are too long.
Power the bus off, then measure between CAN High and CAN Low.
Guideline maxima for ISO 11898-2 high-speed CAN with good twisted pair.
Check a truck or machine network against the SAE physical-layer limits.
Guideline values. Bus length follows the CiA CANopen bit-timing table; TI and other ISO 11898 material quote 40 m at 1 Mbit/s and 200 m at 250 kbit/s. J1939-11 limits (40 m backbone, 30 nodes, 1 m stubs) are widely published; J1939-14 and -15 figures come from secondary sources. Cable, transceivers and sample point change the real limit.
High-speed CAN (ISO 11898-2) is a two-wire differential bus. CAN High and CAN Low run as a twisted pair. At rest (recessive) both lines sit near 2.5 V; when a node drives a dominant bit, CAN High rises to about 3.5 V and CAN Low falls to about 1.5 V, a 2 V difference. Because receivers only look at the difference, the bus shrugs off noise that hits both wires equally.
A CAN bus needs a 120 Ω resistor at each physical end of the backbone — two in total, not one per device. With everything powered off, a meter across CAN High and CAN Low reads about 60 Ω on a healthy bus. About 120 Ω means one terminator is missing; about 40 Ω means there is one too many. Diagnostic ports and adapter cables are stubs, so they must not add a terminator of their own.
CAN is differential, but the transceivers still need a common ground reference within a few volts, so carry a ground (or CAN ground) with the pair. Where a shield is used, ground it at one point only on the whole network to avoid ground loops.
The faster the bus, the shorter it must be: roughly 25–40 m at 1 Mbit/s, 100 m at 500 kbit/s and 250 m at 250 kbit/s. Keep stubs (the branches from the backbone to each device) short — about 0.3 m at 1 Mbit/s, and 1 m on a J1939-11 truck network.
On J1939 vehicle wiring, CAN High is yellow and CAN Low is green. DeviceNet and many industrial M12 cables use white for CAN High and blue for CAN Low. Generic sensor cordsets use a different code entirely, so never wire by colour alone.
On vehicles: the 9-pin Deutsch J1939 diagnostic connector (black Type I and green Type II) on heavy trucks, the 16-pin OBD-II connector on cars and light trucks, and the 3-pin Deutsch DT on J1939 backbones. On interfaces and industrial equipment: the DB9 (D-sub 9), the M12 5-pin A-coded and the RJ45, all with pin assignments recommended by CAN in Automation (CiA).
J1939 9-pin: C and D. OBD-II: 6 and 14. DB9: 7 and 2. 3-pin Deutsch: A and B. M12: 4 and 5. RJ45 (CiA): 1 and 2. Ground is pin A on the 9-pin, 5 (signal) or 4 (chassis) on OBD-II, and 3 on DB9 and RJ45.
Switch the bus off and measure resistance between CAN High and CAN Low. About 60 Ω means two 120 Ω terminators are fitted correctly; about 120 Ω means one is missing; about 40 Ω means one too many.
Yes: 9-pin C (CAN High) to DB9 7, D (CAN Low) to DB9 2, A (ground) to DB9 3. Only connect battery (pin B) to DB9 pin 9 if your interface accepts the truck’s 12 or 24 V. The converter on this page draws the full wiring.
There is none: CAN FD uses the same connectors and pinouts as classic CAN. CiA 106 now covers classic CAN, CAN FD and CAN XL with the same assignments.
Sources: CiA 106 connector pin assignment; HMS / Ixxat CAN connector pin reference; TI SLLA270: CAN physical layer requirements; TI SLOA101: Introduction to CAN; Kvaser: measuring CAN termination; Kvaser: J1939 standards overview; CiA: CANopen lower layers; CSS Electronics: J1939 explained; Wikipedia: CAN bus.
Last reviewed 2026-10-27.
iMatrix designs and builds CAN, J1939 and OBD-II harnesses for OEMs and fleets, and our FleetConnect telematics devices plug straight into the 9-pin and OBD-II ports. Tell us the two ends and the quantity.