Automotive
OBD2 connector pinout
The 16-pin OBD-II diagnostic connector under every car dashboard since the late 1990s: power pins, protocol pins and which ones your vehicle actually uses.
Vehicle socket (female DLC), front view
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Tap or hover any pin to see what it does.
The OBD-II connector, standardised as SAE J1962, has 16 pins in two rows. Pin 16 is always battery positive, pins 4 and 5 are chassis and signal ground, and the rest carry the diagnostic protocols. A car uses only one protocol for its emissions diagnostics, so only some protocol pins are populated in any given vehicle.
Modern vehicles talk CAN on pins 6 and 14; older ones may use the K-line on pin 7 or SAE J1850 on pins 2 and 10. The diagram shows the socket in the car; switch to the tool-plug tab to see the mirror image you would wire into an adapter.
Vehicle socket (female DLC), front view: every pin
| Pin | Name | Function |
|---|---|---|
| 1 | Discretionary | Manufacturer-defined (e.g. GM single-wire CAN / GMLAN; VW-Audi switched ignition +12 V)Not part of generic OBD-II; may be absent. |
| 2 | J1850 Bus + | SAE J1850 PWM bus + (41.6 kbit/s, mostly older Ford); SAE J1850 VPW single-wire bus (10.4 kbit/s, mostly older GM)Only populated on vehicles that use J1850 for emissions diagnostics. |
| 3 | Discretionary | Manufacturer-defined (e.g. Ford DCL +, Chrysler CCD bus +) |
| 4 | Chassis ground | Chassis / power groundReturn path for tool power. Present on every OBD-II socket. |
| 5 | Signal ground | Signal ground (reference for the communication lines)Normally present; a few vehicles have been reported without it - tools then use pin 4. |
| 6 | CAN High | CAN-H for ISO 15765-4 (CAN OBD) and SAE J2284With pin 14 forms the CAN pair; CAN has been mandatory for OBD on US vehicles from model year 2008. |
| 7 | K-Line | ISO 9141-2 and ISO 14230-4 (KWP2000) K-line, single-wire bidirectionalTypical of European and Asian vehicles before CAN. The tester pulls it up to battery voltage through 510 Ω. |
| 8 | Discretionary | Manufacturer-defined |
| 9 | Discretionary | Manufacturer-defined (e.g. older GM 8192-baud ALDL; tachometer/RPM signal on some BMW and Toyota) |
| 10 | J1850 Bus - | SAE J1850 PWM bus - (PWM only; VPW does not use it) |
| 11 | Discretionary | Manufacturer-defined |
| 12 | Discretionary | Manufacturer-defined |
| 13 | Discretionary | Manufacturer-defined |
| 14 | CAN Low | CAN-L for ISO 15765-4 and SAE J2284Pairs with pin 6 (twisted pair). |
| 15 | L-Line | ISO 9141-2 / ISO 14230-4 L-line (optional, used only for initialisation on some cars)Many K-line vehicles do not need it. |
| 16 | Battery + | Unswitched battery positive: +12 V on Type A sockets, +24 V on Type BNormally live even with the ignition off, so plug-in dongles left connected can drain the battery. |
Scan-tool plug (male), front view: every pin
| Pin | Name | Function |
|---|---|---|
| 1 | Discretionary | Manufacturer-defined (e.g. GM single-wire CAN / GMLAN; VW-Audi switched ignition +12 V)Not part of generic OBD-II; may be absent. |
| 2 | J1850 Bus + | SAE J1850 PWM bus + (41.6 kbit/s, mostly older Ford); SAE J1850 VPW single-wire bus (10.4 kbit/s, mostly older GM)Only populated on vehicles that use J1850 for emissions diagnostics. |
| 3 | Discretionary | Manufacturer-defined (e.g. Ford DCL +, Chrysler CCD bus +) |
| 4 | Chassis ground | Chassis / power groundReturn path for tool power. Present on every OBD-II socket. |
| 5 | Signal ground | Signal ground (reference for the communication lines)Normally present; a few vehicles have been reported without it - tools then use pin 4. |
| 6 | CAN High | CAN-H for ISO 15765-4 (CAN OBD) and SAE J2284With pin 14 forms the CAN pair; CAN has been mandatory for OBD on US vehicles from model year 2008. |
| 7 | K-Line | ISO 9141-2 and ISO 14230-4 (KWP2000) K-line, single-wire bidirectionalTypical of European and Asian vehicles before CAN. The tester pulls it up to battery voltage through 510 Ω. |
| 8 | Discretionary | Manufacturer-defined |
| 9 | Discretionary | Manufacturer-defined (e.g. older GM 8192-baud ALDL; tachometer/RPM signal on some BMW and Toyota) |
| 10 | J1850 Bus - | SAE J1850 PWM bus - (PWM only; VPW does not use it) |
| 11 | Discretionary | Manufacturer-defined |
| 12 | Discretionary | Manufacturer-defined |
| 13 | Discretionary | Manufacturer-defined |
| 14 | CAN Low | CAN-L for ISO 15765-4 and SAE J2284Pairs with pin 6 (twisted pair). |
| 15 | L-Line | ISO 9141-2 / ISO 14230-4 L-line (optional, used only for initialisation on some cars)Many K-line vehicles do not need it. |
| 16 | Battery + | Unswitched battery positive: +12 V on Type A sockets, +24 V on Type BNormally live even with the ignition off, so plug-in dongles left connected can drain the battery. |
Key facts
- SAE J1962 (the same connector is ISO 15031-3) defines the 16-pin diagnostic link connector. The vehicle carries the female socket; scan tools and dongles carry the male plug.
- Numbering on the vehicle socket face: 1-8 across the wider top row from left to right, 9-16 across the bottom row from left to right.
- Power: pin 16 is unswitched battery positive, pin 4 chassis ground, pin 5 signal ground. A tool can run entirely from the socket.
- Type A connectors are for 12 V vehicles (cars, light trucks) and have a continuous centre groove. Type B connectors are for 24 V vehicles and have the groove interrupted in the middle, so a 12 V-only Type A tool cannot be plugged into a 24 V vehicle; a Type B tool fits both.
- CAN (ISO 15765-4): CAN-H on pin 6, CAN-L on pin 14, at 250 or 500 kbit/s with 11-bit or 29-bit identifiers. Generic requests go to ID 0x7DF and the engine ECU usually answers on 0x7E8.
- K-line protocols (ISO 9141-2, ISO 14230-4 KWP2000): K-line on pin 7, optional L-line on pin 15, 10.4 kbit/s typical.
- SAE J1850: PWM (41.6 kbit/s) uses pins 2 (+) and 10 (-); VPW (10.4 kbit/s) uses pin 2 only.
- A vehicle uses one of these protocols for its emissions diagnostics, so only some of the protocol pins are populated in any given car. CAN has been mandatory on US vehicles since the 2008 model year.
- Pins 1, 3, 8, 9, 11, 12 and 13 are left to the manufacturer (proprietary buses, ignition feeds, programming lines). Do not assume their function across brands.
- OBD-II became mandatory for US cars and light trucks from the 1996 model year; the EU equivalent (EOBD) applies to petrol cars from 2001 and diesels from 2003-2004.
- The socket must be within easy reach of the driver - typically under the dashboard near the steering column (US rules: within about 2 ft of the steering wheel unless an exemption is granted).
- Pin 16 stays live with the ignition off on most vehicles, so a permanently plugged-in dongle can slowly drain the battery.
Sources
Pin assignments were checked against these references on 2026-10-14. The diagram is our own drawing.
- Wikipedia - On-board diagnostics (OBD-II diagnostic connector section)
- Elm Electronics - ELM327 datasheet (Example Applications, Figures 8-9)
- CSS Electronics - OBD2 Explained: A Simple Intro
Questions people ask
Which OBD2 pin is 12 V?
Pin 16 is unswitched battery positive. Pins 4 and 5 are chassis ground and signal ground.
Which pins does CAN bus use on OBD2?
CAN-High is pin 6 and CAN-Low is pin 14 (ISO 15765-4).
Why does my OBD2 scanner not connect?
Check pin 16 for battery voltage and pins 4/5 for ground first; then that the scanner supports your vehicle’s protocol. Many cheap adapters also struggle with older K-line vehicles.
What is the difference between OBD2 Type A and Type B?
Type A is for 12 V vehicles and has a continuous centre groove; Type B is for 24 V vehicles and has an interrupted groove so a 12 V tool can’t be plugged in by mistake.