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Professional 909X User Manual
components. These components were causing an increase in emissions.
• Because OBD I systems only detect failed components, the degraded
components were not setting codes.
• Some emissions problems related to degraded components only occur
when the vehicle is being driven under a load. The emission checks being
conducted at the time were not performed under simulated driving conditions.
As a result, a signicant number of vehicles with degraded components were
passing Emissions Tests.
• Codes, code definitions, diagnostic connectors, communication protocols
and emissions terminology were different for each manufacturer. This caused
confusion for the technicians working on different make and model vehicles.
To address the problems made evident by this study, CARB and the EPA passed
new laws and standardization requirements. These laws required that vehicle
manufacturers to equip their new vehicles with devices capable of meeting
all of the new emissions standards and regulations. It was also decided that
an enhanced on-board diagnostic system, capable of addressing all of these
problems, was needed. This new system is known as “On-Board Diagnostics
Generation Two (OBD II).” The primary objective of the OBD II system is to
comply with the latest regulations and emissions standards established by CARB
and the EPA.
The Main Objectives of the OBD II System are:
• To detect degraded and/or failed emissions-related components or systems
that could cause tailpipe emissions to exceed by 1.5 times the Federal Test
Procedure (FTP) standard.
• To expand emissions-related system monitoring. This includes a set of
computer run diagnostics called Monitors. Monitors perform diagnostics and
testing to verify that all emissions-related components and/or systems are
operating correctly and within the manufacturer’s specications.
• To use a standardized Diagnostic Link Connector (DLC) in all vehicles.
(Before OBD II, DLCs were of different shapes and sizes.)
• To standardize the code numbers, code definitions and language used to
describe faults. (Before OBD II, each vehicle manufacturer used their own
code numbers, code denitions and language to describe the same faults.)
• To expand the operation of the Malfunction Indicator Lamp (MIL).
• To standardize communication procedures and protocols between the
diagnostic equipment (Diagnostic Tools, Code Readers, etc.) and the
vehicle’s on-board computer.