OBD-II connector pinout and location

The OBD-II port is a 16-pin, D-shaped socket defined by SAE J1962 (its ISO equivalent is ISO 15031-3). Pin 16 brings battery power, pins 4 and 5 are ground, and the data pins depend on which communication protocol the vehicle uses. Since the 2008 model year, US cars and light and medium-duty trucks talk on CAN, through pins 6 and 14.

The drawing shows the socket in the car, seen from the front. Pins 1 to 8 are the top row, left to right. Pins 9 to 16 are the bottom row. Pins with an assigned function are filled in. The others are left to the manufacturer.

Pinout

"Manufacturer discretionary" means the standard leaves the pin to the vehicle maker. None of the standard OBD-II protocols use these pins.

Which pins each protocol uses

An OBD-II vehicle uses one of five standard protocols for its emission-related data. (Heavy-duty trucks use SAE J1939 instead.)

Every protocol also uses pin 16 for power and pins 4 and 5 for ground. Many ISO 9141-2 and ISO 14230-4 vehicles do not use the L-line on pin 15. Some need it to start communication.

Seeing which pin positions have metal contacts can hint at the protocol, but it does not prove it, because makers can fit discretionary pins for their own use. A scan tool or ELM327 adapter set to automatic protocol search finds the right one by itself.

Where is the OBD-II port?

For vehicles certified to California's OBD II rule from the 2004 model year onward (nearly all US vehicles), the location is fixed:

• In the driver's side footwell, between the driver's door side and the driver's edge of the center console.
• No higher than the bottom of the steering wheel in its lowest position.
• Not on or in the center console.
• Easy for a technician crouching at the driver's door to find.
• If it has a cover, the cover must come off by hand without tools and carry a label. You must not have to open or remove a storage tray or ashtray to reach it.

In the EU, the socket's position must be agreed with the type-approval authority. It must be easy for service staff to reach but protected from tampering.

If you cannot find the socket, the owner's manual or the service information for your vehicle shows where it is.

Power on the port

• Pin 16 is wired to the battery and usually stays live with the ignition off. An adapter left plugged in keeps drawing a small current, so unplug it if the car will sit unused for days.
• Power pins must be fused, and they may not exceed 20 volts DC, whatever the vehicle's system voltage.
• If the tool does not power up, check the fuse that feeds the port. Codes such as P0562 (system voltage low) and P0563 (system voltage high) relate to the supply the computer sees.

The port is OBD-II, but the car may not be

General Motors' pre-OBD-II diagnostics used the Assembly Line Diagnostic Link (ALDL), originally on a 12-pin connector. Some GM vehicles from just before OBD-II (mainly 1994–1995) had a 16-pin socket that looks like the OBD-II one but still spoke ALDL, a protocol OBD-II tools do not support. If a pre-1996 vehicle has a 16-pin socket, check the label under the hood for "OBD II" before buying a tool. See what is OBD-II for which vehicles have it.

When the tool will not connect

• Turn the ignition on before you connect.
• Check that the plug is fully seated; the socket is keyed and goes in one way only.
• Check the fuse that feeds the port. The fuse chart in the owner's manual may list it.
• On a CAN vehicle, a network fault can stop modules from answering. Codes in the U0100 range, such as U0100, mean one module lost communication with another.

For the terms on this page, see the OBD-II glossary. For what the tool reads once it connects, see how to read an OBD-II code.

OBD DashX works with ELM327 adapters that plug into this port and pair over classic Bluetooth on Android. See which adapters work.