Chrysler 2005 Sebring, Руководство по обслуживанию, Страница: 2158 / 3204

richer than optimum A/F mixture or vice versa. As
the PCM adjusts the air/fuel ratio, the sensor must
be able to rapidly detect the change. As the sensor
ages, it could take longer to detect the changes in the
oxygen content of the exhaust gas. The rate of
change that an oxygen sensor experiences is called
’Big Slope’. The PCM checks the oxygen sensor volt-
age in increments of a few milliseconds.
Re d u c e d Ou tp u t Vo lta g e (Ha lf Cy c le )—
The
output voltage of the O2S ranges from 0 to 1 volt. A
good sensor can easily generate any output voltage in
this range as it is exposed to different concentrations
of oxygen. To detect a shift in the A/F mixture (lean
or rich), the output voltage has to change beyond a
threshold value. A malfunctioning sensor could have
difficulty changing beyond the threshold value. Many
times the condition is only temporey and the sensor
will recover. Under normal conditions the voltage sig-
nal surpasses the threshold, and a counter is incre-
mented by one. This is called the Half Cycle Counter.
He a te r P e rfo rm a n c e —
The heater is tested by a
separate monitor. Refer to the Oxygen Sensor Heater
Monitor.
OP ERATION —
As the Oxygen Sensor signal
switches, the PCM monitors the half cycle and big
slope signals from the oxygen sensor. If during the
test neither counter reaches a predetermined value, a
malfunction is entered and a Freeze Frame is stored.
Only one counter reaching its predetermined value is
needed for the monitor to pass.
The Oxygen Sensor Signal Monitor is a two trip
monitor that is tested only once per trip. When the
Oxygen Sensor fails the test in two consecutive trips,
the MIL is illuminated and a DTC is set. The MIL is
extinguished when the Oxygen Sensor monitor
passes in three consecutive trips. The DTC is erased
from memory after 40 consecutive warm-up cycles
without test failure.
En a blin g Co n d itio n s —
The following conditions
must typically be met for the PCM to run the oxygen
sensor monitor:
•
Battery voltage
•
Engine temperature
•
Engine run time
•
Engine run time at a predetermined speed
•
Engine run time at a predetermined speed and
throttle opening
•
Transmission in gear (automatic only)
•
Fuel system in Closed Loop
•
Long Term Adaptive (within parameters)
•
Power Steering Switch in low PSI (no load)
•
Engine at idle
•
Fuel level above 15%
•
Ambient air temperature
•
Barometric pressure
•
Engine RPM within acceptable range of desired
idle
•
Closed throttle speed
P e n d in g Co n d itio n s —
The Task Manager typi-
cally does not run the Oxygen Sensor Signal Monitor
if overlapping monitors are running or the MIL is
illuminated for any of the following:
•
Misfire Monitor
•
Front Oxygen Sensor and Heater Monitor
•
MAP Sensor
•
Vehicle Speed Sensor
•
Engine Coolant Temperature Sensor
•
Throttle Position Sensor
•
Engine Controller Self Test Faults
•
Cam or Crank Sensor
•
Injector and Coil
•
Idle Air Control Motor
•
EVAP Electrical
•
EGR Solenoid Electrical
•
Intake Air Temperature
•
5 Volt Feed
Co n flic t—
The Task Manager does not run the
Oxygen Sensor Monitor if any of the following condi-
tions are present:
•
A/C ON (A/C clutch cycling temporarily sus-
pends monitor)
•
Purge flow in progress
•
Ethenal content learn is taking place and the
ethenal used once flag is set
S u s p e n d —
The Task Manager suspends maturing
a fault for the Oxygen Sensor Monitor if an of the fol-
lowing are present:
•
Oxygen Sensor Heater Monitor, Priority 1
•
Misfire Monitor, Priority 2
OXYGEN SENSOR HEATER MONITOR (NGC)
D ES CRIP TION —
If the Oxygen sensor (O2S) DTC
as well as a O2S heater DTC is present, the O2S
Heater DTC MUST be repaired first. After the O2S
Heater is repaired, verify that the sensor circuit is
operating correctly.
The voltage reading taken from the O2S are very
temperature sensitive. The readings taken from the
O2S are not accurate below 300 degrees C. Heating
the O2S is done to allow the engine controller to shift
to closed loop control as soon as possible. The heating
element used to heat the O2S must be tested to
ensure that it is heating the sensor properly. Starting
with the introduction on the NGC module the strat-
egy for checking the heater circuit has changed. The
heater resistance is checked by the NGC almost
immediately after the engine is started. The same
O2S heater return pin used to read the heater resis-
tance is capable of detecting an open circuit, a
shorted high or shorted low condition.
JR
EMISSIONS CONTROL 25 - 3
EMISSIONS CONTROL (Continued)