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. In today's vehicles, it's in constant communication with the CAN, or Computer Area Network. It provides a standard connection for automotive technicians to tap into and diagnose different onboard computers.
This is great because OBD I vehicles have different proprietary connections that require several different types of connectors to tap into. OBD II connectors are located in the passenger's compartment close to the steering wheel for easy access from the driver's side, passenger side, or from outside the vehicle. An OBD I connector may be located in other areas such as the engine compartment.
Some pins function is standard and required by all manufacturers, while other pins are left to the individual manufacturer's discretion. For instance, the CAN network's resistance can be checked with the key off through pins 6 and 14.
Today's vehicles have many onboard computer modules dedicated to different tasks throughout the vehicle. Tapping into this valuable diagnostic information has been located in this one convenient place. 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.