Actron OBD II AutoScanner CP9135 Instructions Manual page 30

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.
A-2
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,
Glossary