OBDII Scanner Tool User's Manual

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.

source