Appendix b about obd ii, About obd, Appendix b – Actron CP9135 OBD II AutoScanner User Manual
Page 30
B-1
About OBD II
OBD II
In
1994,
manufacturers
began
equipping
vehicles
with
a
new
class
of
computer
technology
which
puts
more
processing
power
in
the
vehicle
than
ever
before.
It
is
called
On-Board
Diagnostics,
Second
Generation
(OBD
II)
and
offers
increased
system
monitoring
and
diagnostic
information.
Beginning
January 1,
1996,
vehicles
sold
in
the
U.S.
are
required
to
be
OBD
II
compliant.
However,
a
few
vehicles
were
exempt
since
no
changes
were
made
to
the
engine.
Most
domestic
manufacturers
began
using
this
system
on
some
vehicles
beginning
as
early
as
1994.
OBD
II
systems
are
designed
to
meet
or
exceed
standards
and
regulations
to
improve
air
quality.
These
standards
and
regulations
are
primarily
set
forth
by
the
Environmental
Protection
Agency
(EPA)
Clean
Air
Act
of
1990.
Most
of
the
standards
and
regulations
were
developed
by
the
California
Air
Resources
Board
(CARB).
OBD
II
systems
are
unique
in
that
they
possess
the
capability
of
monitoring
the
performance
of
emission
related
systems
and
their
components;
to
detect
hard
and
intermittent
faults
that
may
cause
a
vehicle
to
pollute.
This
new
system
stores
a
large
library
of
general
trouble
codes
along
with
manufacturer-specific
codes,
some
of
which
can
be
accessed
with
the
tool.
These
codes
cover:
Now,
basic
terms
are
standardized
and
all
generic
(global)
codes
share
a
common
format
and
terminology
established
by
the
manufacturers
and
the
Society
of
Automotive
Engineers
(SAE).
Basics of Computer-Controlled Vehicles
This
section
explains
the
engine
computer
control
system,
the
types
of
sensors
and
how
the
computer
controls
engine
fuel
delivery,
idle
speed
and
timing.
Additional
information
may
be
found
in
technical
support
books
at
your
local
library
or
auto
parts
store.
The
more
you
know
about
the
computer
system,
the
better
you
can
diagnose
vehicle
computer
problems.
Computer
controls
were
originally
installed
on
vehicles
to
meet
federal
government
regulations
for
lower
emissions
levels
and
improved
fuel
economy.
This
began
in
the
early
1980’s
when
basic
mechanical
systems
were
no
longer
able
to
accurately
control
key
engine
parameters.
A
computer
could
be
programmed
to
control
the
engine
under
various
operating
conditions,
making
the
engine
more
reliable.
While
these
early
systems
were
very
limited
in
the
scope
of
their
control,
providing
only
10
to
14
trouble
codes,
they
did
help
guide
the
vehicle
repair
process.
Today,
computer
controls
have
made
cars
and
trucks
faster,
cleaner,
and
more
efficient
than
ever
before.
B-Codes . . . . . . . Body
Systems
C-Codes . . . . . Chassis
Systems
U-Codes . Network
Communications
P-Codes . . . . . . Powertrain
Systems
Appendix B
About OBD
II