Introduction To On-Board Diagnostics - Actron CP9190 User Manual

Getting Started

Introduction to On-Board Diagnostics

OBD I
The original on-board diagnostics (OBD I) lacked consistency in
communication and interface while allowing different interpretations
among vehicle manufacturers. Ford and Chrysler used different types
of engine control computers and data link connectors ( DLCs), and GM
varied the trouble codes and communication protocols from
year-to-year.
OBD II
2
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.
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