Actron CP9035 Insrucciones página 48

REFERENCE GLOSSARY
EGR system injects exhaust gases
into the intake manifold to reduce these
gases at the tailpipe.
O2S:
Oxygen Sensor. The oxygen sensor is
threaded into the exhaust manifold,
directly in the stream of exhaust gases.
The PCM uses the sensor to "fine tune"
fuel delivery. The sensor generates a
voltage of 0.6 to 1.1 volts when the
exhaust gas is rich (low oxygen
content). The voltage changes to 0.4
volts or less when the exhaust gas is
lean (high oxygen content). The sensor
only operates after it reaches a
temperature of approximately 349°C
(660°F).
ODM:
Output Device Monitor.
On-Board Diagnostics, Phase II
(OBD II):
With the passing of the 1990 Clean Air
Act Amendment, the EPA imposed
more stringent requirements. These
requirements include the addition of
multiple oxygen sensors, one before
the catalytic converter and one after to
provide the PCM with information on
catalyst efficiency and condition. There
are also computer-controlled EGR, fuel
pressure regulators, and smart ignition
systems. Additionally, OBD II requires a
common data connector and connec-
tor location. Further requirements
include an industry-standard data
message, defined by both an industry
committee of engineers from most
major manufacturers and the SAE.
Vehicle manufacturers are required by
law to provide at least a minimum
amount of data for emissions pro-
grams to access the critical emissions
data available through OBD II. OBD II
began to appear in vehicles in late
1994, and is supposed to be equip-
ment on all cars sold in the US after
January 1, 1996.
8-7
Open (Circuit):
A break in the continuity of a circuit
such that no current may flow through
it.
Open Loop (O/L):
This is when the control system
performs an action (expecting a certain
result), but has no way of verifying if the
desired results were achieved.
Example: The PCM operates a fuel
injector expecting a certain amount of
fuel to be delivered (The PCM assumes
everything in the fuel system is
performing properly). In open loop
operation, the PCM has no way of
checking the actual amount of fuel
delivered. Thus, a faulty fuel injector or
incorrect fuel pressure can change the
amount of fuel delivered and the PCM
would not know it. In general, a control
system operates in open loop mode
only when there is no practical way to
monitor the results of an action.
Example: Fuel delivery during cold
engine warm-up. The computer runs in
open loop mode because the oxygen
sensor is not ready to send a signal.
Without the sensor signal, the com-
puter cannot check the actual amount
of fuel delivered.
Outputs:
Electrical signals sent from the PCM.
These signals may activate relays or
other actuators for control purposes
throughout the vehicle. The signals can
also send information from the PCM to
other electronic modules, such as the
ignition or trip computer.
P/N:
Park/Neutral Switch. This switch tells
the PCM when the gear shift lever is in
the Park or Neutral position. Then the
PCM will operate the engine in an "idle"
mode.
PCM: