Glossary
A-5
Sensor:
Any
device
that
reports
information
to
the
PCM.
The
job
of
the
sensor is
to
convert
a
parameter
such
as
engine
temperature
into
an
electrical
signal
that
the
PCM
can
understand.
Sensor 1:
A
standard
term
used
to
identify
the
location
of
oxygen
sensors. Sensor 1 is
located
upstream
of
the
catalytic
converter.
See
O2S
,
Bank
1
,
Bank
2
.
Sensor 2:
A
standard
term
used
to
identify
the
location
of
oxygen
sensors. Sensor 2 is
located
downstream
of
the
catalytic
converter.
See
O2S
,
Bank
1
,
Bank
2
.
SFI
or
SEFI:
Sequential
Fuel
Injection
or
Sequential
Electronic
Fuel
Injection.
A
fuel
injection
system
that
uses
one
or
more
injectors
for
each
cylinder.
The
injectors
are
mounted
in
the
intake
manifold,
and
are
fired
individually.
ST:
Short
Term
fuel
trim.
TBI:
Throttle
Body
Injection.
A
fuel
injection
system
having
one
or
more
injectors
mounted
in
a
centrally
located
throttle
body,
as
opposed
to
positioning
the
injectors
close
to
an
intake
valve
port.
TBI
is
also
called
Central
Fuel
Injection
(CFI)
in
some
vehicles.
TDC:
Top
Dead
Center.
When
a
piston
is
at
its
uppermost
position
in
the
cylinder.
Throttle
Body:
A
device
which
performs
the
same
function
as
a
carburetor
in
a
fuel
injection
system.
On
a
throttle
body
injection
(TBI)
system,
the
throttle
body
is
both
the
air
door
and
the
location
of
the
fuel
injectors.
On
port
fuel
injection
systems
(PFI,
MPFI,
SFI,
etc.)
the
throttle
body
is
simply
an
air
door.
Fuel
is
not
added
until
the
injectors
at
each
intake
port
are
activated.
In
each
case,
the
throttle
body
is
attached
to
the
accelerator
pedal.
TPS:
Throttle
Position
Sensor.
Potentiometer-type sensor connected
to
the
throttle
shaft.
Its
voltage
signal
output
increases
as
the
throttle
is
opened.
The
PCM
uses
this
signal
to
control
many
systems
such
as
idle
speed,
spark
advance,
fuel
delivery,
etc.
TTS:
Transmission
Temperature
Sensor.
A
resistance
sensor mounted
in
the
transmission
housing
in
contact
with
the
transmission
fluid.
It
sends
a
voltage
signal
to
the
PCM
indicating
the
temperature
of
the
transmission.
VECI:
Vehicle
Emission
Control
Information.
A
decal
located
in
the
engine
compartment
containing
information
about
the
emission
control
systems
found
on
the
vehicle.
The
VECI
is
the
authoritative
source
for
determining
whether
a
vehicle
is
OBD
II
compliant.
VIN:
Vehicle
Identification
Number.
This
is
the
factory-assigned
vehicle
serial
number.
This
number
is
stamped
on
a
number
of
locations
throughout
the
vehicle,
but
the
most
prominent
location
is
on
top
of
the
dashboard
on
the
driver’s
side,
visible
from
outside
the
car.
The
VIN
includes
information
about
the
car,
including
where
it
was
built,
body
and
engine
codes,
options,
and
a
sequential
build
number.
VSS:
Vehicle
Speed
Sensor.
Sends
a
frequency
signal
to
the
PCM.
The
frequency
increases
as
the
vehicle
moves
faster
to
give
the
PCM
vehicle
speed
information
used
to
determine
shift
points,
engine
load,
and
cruise
control
functions.
WOT:
Wide-Open
Throttle.
The
vehicle
operating
condition
brought
about
when
the
throttle
is
completely
(or
nearly)
open.
The
PCM
will
typically
deliver
extra
fuel
to
the
engine
and
de-energize
the
A/C
compressor
at
this
time
for
acceleration
purposes.
The
PCM
uses
a
switch
or
the
Throttle
Position
Sensor to
identify
the
WOT
condition.
