Actron CP9135 OBD II AutoScanner User Manual
Page 28
A-4
Glossary
NOx:
Oxides
of
Nitrogen.
A
pollutant.
The
EGR
system
injects
exhaust
gases
into
the
intake
manifold
to
reduce
these
gases
at
the
tailpipe.
O2S:
Oxygen
Sensor.
Generates
a
voltage
of
0.6
to
1.1
volts
when
the
exhaust
gas
is
rich
(low
oxygen
content).
The
voltage
changes
to
0.4
volts
or
less
when
the
exhaust
gas
is
lean
(high
oxygen
content).
This
sensor only
operates
after
it
reaches
a
temperature
of
approximately
349°C
(660°F).
O2
sensors
are
usually
found
both
upstream
and
downstream
of
the
catalytic
converter.
The
PCM
uses
these
sensors
to
fine
tune
the
air-fuel
ratio
and
to
monitor
the
efficiency
of
the
catalytic
converter.
See
Bank
1,
Bank
2,
Sensor 1, Sensor 2.
ODM:
Output
Device
Monitor.
OBD
II:
On-Board
Diagnostics,
Second
Generation.
OBD
II
is
a
U.S.
Government-mandated
standard
requiring
all
cars
and
light
trucks
to
have
a
common
data
connector,
connector
location,
communication
protocol,
DTCs
and
code
definitions.
OBD
II
first
appeared
on
vehicles
in
late
1994,
and
is
required
to
be
present
on
all
cars
sold
in
the
US
after
January
1,
1996.
Open
Loop
(O/L):
A
control
system
mode
that
does
not
monitor
the
output
to
verify
if
the
desired
results
were
achieved.
A
fuel
delivery
system
will
usually
operate
in
open
loop
mode
during
cold
engine
warm-up
because
the
oxygen
sensors
are
not
yet
ready
to
send
a
signal.
Without
the
oxygen sensor signal,
the
computer
cannot
check
the
actual
results
of
combustion.
P/N:
Park/Neutral
Switch.
This
switch
tells
the
PCM
when
the
gear
shift
lever
is
in
the
Park
or
Neutral
position.
When
in
Park
or
Neutral,
the
PCM
will
operate
the
engine
in
an
“idle”
mode.
PCM:
Powertrain
Control
Module.
The
“brains”
of
the
engine
control
system
housed
in
a
metal
box
with
a
number
of
sensors
and
actuators
connected
via
a
wiring
harness.
Its
job
is
to
control
fuel
delivery,
idle
speed,
spark
advance
timing,
and
emission
systems.
The
PCM
receives
information
from
sensors,
then
energizes
various
actuators
to
control
the
engine.
The
PCM
is
also
known
as
the
ECM
(Engine
Control
Module).
PROM:
Programmable
Read-Only
Memory.
The
PROM
contains
programming
information
the
PCM
needs
to
operate
a
specific
vehicle
model/engine
combination.
Pending
Codes:
Also
referred
to
as
Continuous
Memory
codes
and
Maturing
Diagnostic
Trouble
codes.
These
codes
are
set
when
intermittent
faults
occur
while
driving.
If
the
fault
does
not
occur
after
a
certain
number
of
drive
cycles,
the
code
is
erased
from
memory.
Purge
Solenoid:
Controls
the
flow
of
fuel
vapors
from
the
carbon
canister
to
the
intake
manifold.
The
canister
collects
vapors
evaporating
from
the
fuel
tank,
preventing
them
from
escaping
to
the
atmosphere
and
causing
pollution.
During
warm
engine
cruise
conditions,
the
PCM
energizes
the
Purge
Solenoid
so
the
trapped
vapors
are
drawn
into
the
engine
and
burned.
Reluctance
Sensor:
A
type
of sensor typically
used
to
measure
crankshaft
or
camshaft
Speed
and/or
position,
driveshaft
speed,
and
wheel
speed
ROM:
Read-Only
Memory.
Permanent
programming
information
stored
inside
the
PCM,
containing
the
information
the
PCM
needs
to
operate
a
specific
vehicle
model/engine
combination.
SAE:
Society
of
Automotive
Engineers.