Every vehicle manufactured since 1996 will have a 16-pin OBD-II connector that can be found within 1 meter (3 feet) of the steering wheel. The image below illustrates what the connector looks like.

You can determine which protocol is implemented by taking a look at the vehicle’s OBD-II connector. All vehicles are required to have pins 4, 5, and 16. Pin 4 is the vehicle’s chassis ground, pin 5 is the signal ground, and pin 16 is positive from the battery. In addition to pins 4, 5, and 16, the connector will have one or more pins. You can use the pin positions to determine which protocol is used on the vehicle.

As a general rule of thumb, you can usually go by the following to determine which protocol your vehicle uses: