Specifications
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 Ter m 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.