Getting Started2 – 6 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •2Introduction to On-Board DiagnosticsOBD IThe original on-board diagnostics (OBD I) lacked consistency incommunication and interface while allowing different interpretationsamong vehicle manufacturers. Ford and Chrysler used different typesof engine control computers and data link connectors ( DLCs), and GMvaried the trouble codes and communication protocols fromyear-to-year.OBD IIOn-board diagnostics version II (OBD II) is a system that the Society ofAutomotive Engineers (SAE) developed to standardize automotiveelectronic diagnosis.Beginning in 1996, most new vehicles sold in the United States werefully OBD II compliant.✓ Technicians can now use the same tool to test any OBD IIcompliant vehicle without special adapters. SAE establishedguidelines that provide:❒ A universal connector, called the DLC, with dedicated pinassignments.❒ A standard location for the DLC, visible under the dash on driver’sside.❒ A standard list of diagnostic trouble codes (DTCs) used by allmanufacturers.❒ A standard list of parameter identification (PID) data used by allmanufacturers.❒ Ability for vehicle systems to record operating conditions when afault occurs.❒ Expanded diagnostic capabilities that records a code whenever acondition occurs that affects vehicle emissions.❒ Ability to clear stored codes from the vehicle’s memory with aScan Tool.
