Actron CP9035 Insrucciones página 44

REFERENCE GLOSSARY
detonation indicates extreme cylinder
pressures or "hotspots" which are
causing the air/fuel mixture to detonate
early. High cylinder pressures may be
caused by excessive load (trailer
towing, A/C operation, etc.) or by
excessive spark advance. High octane
fuel has a higher resistance to
uncontrolled ignition, and may be used
to control detonation when the PCM is
unable to retard timing sufficiently to
prevent it from occurring. NOTE: High
octane fuel is not a cure for the
problem, only the symptom. If your
vehicle experiences long-term detona-
tion, check for other causes.
Diagnostic trouble codes:
Diagnostic Trouble Codes (DTC)
indicate a malfunction flagged by a
vehicle computer. The computer will
display a corresponding code based on
a lookup table in the program of the on-
board computer. Most systems have
the ability to store codes in memory,
which are commonly referred to as
"history codes" or "soft codes."
Malfunctioning circuits will generate
continuous Check Engine lamp
illumination, called "current codes" or
"hard codes." OBD II Systems will
transmit many more DTCs than the
past systems, and therefore will allow
a technician the ability to better pin-
point failures and past events. They
only way to clear codes on OBD II
systems will be with a scan tool that
has the proper programming to
perform the function.
Digital Signal:
An electronic signal which has only two
(2) voltage values: a "low" value (close
to zero) and a "high" value (usually 5
volts or more). Sometimes the low
voltage condition is called OFF and the
high voltage condition is called ON.
Signals which can have any voltage
value are called "analog" signals.
8-3
DIS:
Distributorless Ignition System or
Direct Ignition System. A system that
produces the ignition spark without the
use of a distributor.
Driver:
A transistor "switch" inside the PCM
used to apply power to an external
device. This allows the PCM to control
relays, solenoids, and small motors.
Duty Cycle:
A term applied to frequency signals —
those which are constantly switching
between a small voltage value (close to
zero) and a larger value (usually 5 volts
or more). Duty cycle is the percentage
of time the signal has a large voltage
value. For example, if the signal is
"high" (large voltage) half of the time,
the duty cycle is 50%. If the signal is
"high" only one fourth of the time, then
the duty cycle is 25%. A duty cycle of
0% means the signal is always at a
"low" value and not changing. A duty
cycle of 100% means the signal is
always at a "high" value and not
changing. The PCM uses duty cycle
type signals when it wants more than
just "on-off" control of an actuator. This
is how it works: 50% duty cycle signal
going to a vacuum switching solenoid
means the solenoid will be "on"
(passing full vacuum) half the time, and
"off" (passing no vacuum) half the time.
The average amount of vacuum
passing through the solenoid will be
one half the full value because the
solenoid is only "on" for half the time.
This signal changes at a rapid rate, as
often as ten times per second. Thus
the PCM can get a vacuum controlled
actuator to move halfway between "no
vacuum" and "full vacuum." Other
positions can be achieved by changing
the duty cycle of the control signal
which in turn changes the average
amount of control vacuum.
DVM: