OBD II Data Link Connector
The DLC or Data Link Connector is an OBD II, 16-pin, standard connector used in all automobiles manufactured since 1996. The ECM's electronic control modules communicate with each other using the CAN protocol. They share information over the CAN bus on the Computer Area Network. The OBD II connector provides a standard connection for automotive technicians to tap into and diagnose different onboard computers.
OBD I vehicles have different proprietary connections, requiring several types of connectors, and may be located in areas like the engine compartment. OBD II connectors are located in the passenger compartment close to the steering wheel for easy access. Tapping into this valuable diagnostic information has been located in this one convenient place.
As seen in the pinout above, the different pins in the connector have different functions. Some pin's function is standard and required by all manufacturers. Other pins are left to the individual manufacturer's discretion.
The CAN network's resistance (~60 Ohms) can be checked with the key off through pins 6 and 14 on networks that do not contain a gateway.
Today's vehicles have many onboard computer modules dedicated to different tasks throughout the vehicle. Not all scanners are capable of retrieving all the different types of data. Most scanners must be updated to diagnose different years, makes, and models.