OBD data link connector (DLC) is the multi-pin diagnostic connection port for automobiles, trucks, and motorcycles used to interface a scan tool with the control modules of a given vehicle and access on-board diagnostics and live data streams.

The location of the diagnostic link connector (DLC) on earlier OBD-I vehicles was often a mystery. Many manufacturers located the connector in roughly the same place on each model, but not always. Prior to 1996, there was no standardization for these connectors, and each manufacturer had its own shape with a unique pin arrangement. After 1996, many manufacturers retained their proprietary connectors in addition to the OBD-II interface, because OBD-II ports are only required to transmit emission-related codes and data.

With newer OBD-II systems today Automakers must follow rules, specifically, standard SAE J-1962, regarding placement of a DLC. Every DLC must be in a centralized location within a vehicle’s passenger compartment, and it the standard 16-pin OBD-II diagnostic link connector (DLC) is supposed to be located within 16 inches of the steering wheel. Unfortunately, that’s not always the case. Some automakers do a good job of hiding them behind covers, under center consoles, and inside glove boxes.

Fortunately, once the DLC is located, any OBD-II-capable scan tool or code reader can plug into it and start reading its data. All DLC have a uniform appearance and function, and will connect to any OBD-II-compatible scan tool or code reader.

The picture above illustrates what the 16 pins in a DLC are configured for. Pins 1, 3, 8, 9, 11, 12, and 13 are not assigned to OBD-II functions; rather, these pins are used exclusively by manufacturers for their proprietary information or for enhanced diagnostics. Manufacturers will typically use some combination of these unassigned pins to communicate with dealership service department level scanners and other equipment that uses OEM software.