A-2
Glossary
CKP
REF:
Crankshaft
Position
Reference.
CKP:
Crankshaft
Position.
See
CPS
.
Closed
Loop
(C/L):
A
feedback
system
that
uses
the
O2
sensor(s)
to
monitor
the
results
of
combustion.
Based
on
the
signal(s)
from
the
O2
sensor(s),
the
PCM
modifies
the
air/fuel
mixture
to
maintain
optimum
performance
with
lowest
emissions.
In
closed
loop
mode,
the
PCM
can
“fine
tune”
control
of
a
system
to
achieve
an
exact
result.
CO:
Carbon
Monoxide
Continuous
Memory
Codes:
See
Pending
Codes
.
CPS:
Crankshaft
Position
Sensor.
Sends
a
frequency
signal
to
the
PCM.
It
is
used
to
reference
fuel
injector
operation
and
synchronize
spark
plug
firing
on
distributorless
ignition
systems
(DIS).
CTS:
Coolant
Temperature
Sensor.
A
resistance
sensor
that
sends
a
voltage
signal
to
the
PCM
indicating
the
temperature
of
the
coolant.
This
signal
tells
the
PCM
whether
the
engine
is
“cold”
or
“warm”.
Data
Link
Connector
(DLC):
The
interface
port
between
the
vehicle’s
on-board
computer
and
a
diagnostic
tool.
Vehicles
with
OBD
II
use
a
16-pin
connector
located
in
the
passenger
compartment.
Data
Stream:
The
actual
data
communications
sent
from
the
vehicle’s
PCM
to
the
data
connector.
DEPS:
Digital
Engine
Position
Sensor.
Detonation:
See
Knock
.
DTC:
Diagnostic
Trouble
Code.
Indicates
a
malfunction
flagged
by
the
vehicle’s
computer.
DI/DIS:
Direct
Ignition/Distributorless
Ignition
System.
A
system
that
produces
the
ignition
spark
without
the
use
of
a
distributor.
Duty
Cycle:
A
term
applied
to
signals
that
switch
between
“on”
and
“off”.
Duty
cycle
is
the
percentage
of
time
the
signal
is
“on”.
For
example,
if
the
signal
is
“on”
only
one
fourth
of
the
time,
then
the
duty
cycle
is
25%.
The
PCM
uses
duty
cycle
type
signals
to
maintain
precise
control
of
an
actuator.
ECT:
Engine
Coolant
Temperature
sensor.
See
CTS
.
EFI:
Electronic
Fuel
Injection.
Any
system
where
a
computer
controls
fuel
delivery
to
the
engine
by
using
fuel
injectors.
EGR:
Exhaust
Gas
Recirculation.
The
PCM
uses
the
EGR
system
to
recirculate
exhaust
gases
back
into
the
intake
manifold
to
reduce
emissions.
EGR
Recirculation
is
used
only
during
warm
engine
cruise
conditions.
EGR
flow
at
other
times
can
cause
stalling
or
no
starts.
EPA:
Environmental
Protection
Agency.
ESC:
Electronic
Spark
Control.
An
ignition
system
function
that
warns
the
PCM
when
“knock”
is
detected.
The
PCM
will
then
retard
spark
timing
to
eliminate
the
knocking
condition.
EST:
Electronic
Spark
Timing.
An
ignition
system
that
allows
the
PCM
to
control
spark
advance
timing.
The
PCM
determines
optimum
spark
timing
from
sensor information
—
engine
speed,
