Actron 9640A manual Diagnostic Link Connectors DLC, OBD II J1962

Getting Started

OBD II stands for On-Board Diagnostics version II. OBD II is a system that the Society of Automotive Engineers (SAE) developed to standardize automotive electronic diagnosis. Technicians now can use the same tool to test any OBD

IIcompliant vehicles without special adapters. The SAE established guidelines that provide:

•a universal diagnostic test connector, called the data link connector (DLC), with dedicated pin assignments.

•a standardized location for the DLC, visible under the dash on the driver’s side.

•a standardized list of diagnostic trouble codes (DTCs) used by all manufac- turers.

•a standardized list of parameter identification (PID) data used by all manu- facturers.

•the ability of the vehicle system to record a freeze frame of the operating con- 2 ditions when a fault occurs.

•expanded diagnostic capabilities that records a code whenever a condition occurs that effects vehicle emissions.

•the ability to clear stored codes from vehicle memory with the scan tool.

In addition, SAE has published hundreds of pages of text defining a standard communications protocol that establishes the hardware, software, and circuit parameters of OBD II systems. Unfortunately, vehicle manufacturers have dif- ferent interpretations of this standard communications protocol. As a result, the generic OBD II communications scheme used will vary, depending on the vehi- cle.

SAE publishes recommendations, not laws, but the Environmental Protection Agency (EPA) and California Air Resources Board (CARB) made many of SAE’s recommendations legal requirements that vehicle manufacturers were required to phase in over a three-year period. Beginning in 1994, vehicles with a new engine management computer – about 10% of each manufacturers fleet

–were supposed to comply with OBD II standards. For 1995, OBD II systems were to appear on about 40% of the new vehicles sold in the USA. Some of the 1994-1995 OBD II systems were not fully compliant, so the Government granted waivers to give manufacturers time to fine-tune their systems. Begin- ning in 1996, most of the new vehicles sold in the USA were fully OBD II com- pliant.

DIAGNOSTIC LINK CONNECTORS (DLC)

The Data Link Connector (DLC) allows the scan tool to communicate with the vehicle’s computer(s). Before OBD II, manufacturers used different data link connectors to communicate with the vehicle. The proper DLC adapter cable must be used to connect the tool to the vehicle. Also, the vehicle’s DLC may be found in several different places and have many different configurations. The following describes the DLCs used by Ford, GM and Chrysler. The DLC location and types for domestic vehicles can be looked up in the charts in “Appendix A - Data Link Connectors".

OBD II (J1962)

Beginning in 1996, vehicles sold in the United States use the J1962 (OBD II) DLC, a term taken from a physical and electrical specification number assigned by SAE (J1962). The DLC should be located under

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