Onboard Diagnostics
DIAGNOSTIC TROUBLE CODES (DTCs)
On-Board Diagnostics - Second Generation (OBD 2)
The OBD 2 System is
an enhancement of the
OBD 1 System.
In addition to performing all the functions
of the OBD 1 System, the OBD 2 System
has been enhanced with new Diagnostic
Programs. These programs closely
monitor the functions of various
emissions-related components and systems (as well as other systems)
and make this information readily available (with the proper equipment)
to the technician for evaluation.
The California Air Resources Board (CARB) conducted studies on
OBD 1 equipped vehicles. The information that was gathered from
these studies showed the following:
¾ A large number of vehicles had deteriorating or degraded
emissions-related components. These components were causing an
increase in emissions.
¾ Because OBD 1 systems only detect failed components, the degraded
components were not setting codes.
¾ 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 significant number of vehicles with degraded
components were passing Emissions Tests.
¾ 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 2).” The primary objective of the OBD 2
system is to comply with the latest regulations and emissions standards
established by CARB and the EPA.
The Main Objectives of the OBD 2 System are:
¾ 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.
D900 CanScan 15
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