Daewoo AD100 user manual Introduction to On-Board Diagnostics OBD

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Introduction to On-Board Diagnostics OBD II

On-board diagnostics version II (OBD II) is a system that the Society of Automotive Engineers (SAE) developed to standardize automotive electronic diagnosis.

Beginning in 1996, most new vehicles sold in the United States were fully OBD II compliant.

￿Technicians can now use the same tool to test any OBD II compliant vehicle without special adapters. SAE established guidelines that provide:

￿A universal connector, called the DLC, with dedicated pin assignments.

￿A standard location for the DLC, visible under the dash on driver’s side.

￿A standard list of diagnostic trouble codes (DTCs) used by all manufacturers.

￿A standard list of parameter identification (PID) data used by all manufacturers.

￿Ability for vehicle systems to record operating conditions when a fault occurs.

￿Expanded diagnostic capabilities that records a code whenever a condition occurs that affects vehicle emissions.

￿Ability to clear stored codes from the vehicle’s memory with a Scan Tool.

SAE Publications

SAE has published hundreds of pages of text defining a standard communication protocol that establishes hardware, software, and circuit parameters of OBD II systems.

• 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.