2.
General Information
2.1
On-Board
Diagnostics
(OBD) II
The first generation
of
On·Board Diagnostics (called OBD I) was developed by
the California Air Resources Board (CARB) and implemented
1n
1988 to monitor
some
of
the emission control components on vehicles. As technology evolved
and the desire to improve the On-Board Diagnostic system increased, a new
generation of On-Board Diagnostic system was developed This second
generation
of
On-Board Diagnostic regulations is called "OBD II"
The OBD
II
system is designed to monitor emission control systems and key
engine components by performing either continuous
or
periodic tests
of
specific
components and vehicle conditions. When a problem is detected, the
080
II
system turns on a warning lamp (MIL) on the vehicle instrument panel to alert
the driver typically by the phrase "Check Engine"
or
"Service Engine Soon" The
system will also store important information about the detected malfunction so
that a technician can accurately find and fix the problem Here below follow
three pieces
of
such valuable Information:
1)
Whether the Malfunction Indicator Light (MIL) is commanded 'on'
or
'Off';
2) Which,
if
any, Diagnostic Trouble Codes (DTCs) are stored;
3) Readiness Monitor status.
2.2
Diagnostic
Trouble
Codes
(DTCs)
080
II
Diagnostic Trouble Codes are codes that are stored by the on-board
computer diagnostic system in response to a problem found in the vehicle.
These codes identify a particular problem area and are intended to provide you
with a guide as to where a fault might be occurring within a vehicle. 0
8D
II
Diagnostic Trouble Codes consist
of
a five-digit alphanumeric code. The first
character, a letter, identifies which control system sets the code. The other four
characters, all numbers, provide additional information on where the OTC
originated and the operating conditions that caused it to be set. Below is an
example to illustra
te
the structure
of
the digits·
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