Chrysler PT Cruiser. Manual — part 743
(3) Attach electrical connector to sensor.
(4) Install the negative battery cable.
(5) Install the air cleaner lid and makeup air hose.
INSTALLATION - 1.6L
(1) Make sure that the manifold is clean.
(2) Install sensor to manifold (Fig. 38).
(3) Tighten screws.
(4) Connect the electrical connetor to the sensor.
(5) Connect the negative battery cable
(6) Install the air cleaner cover.
O2 SENSOR
DESCRIPTION
The upstream oxygen sensor (Fig. 41) threads into
the outlet flange of the exhaust manifold (Fig. 39).
The downstream heated oxygen sensor threads into
the system depending on emission package (Fig. 40).
Federal package the O2s is mounted after the cata-
lytic convertor.
OPERATION
A seperate upstream and downstream grounds are
used on the NGC vehicles (4 Cyl.).
As vehicles accumulate mileage, the catalytic con-
vertor deteriorates. The deterioration results in a
less efficient catalyst. To monitor catalytic convertor
Fig. 37 MAP Sensor
1 - MAP SENSOR
Fig. 38 IGNITION COIL, PCV, MAP SENSOR
1 - MAP Sensor
2 - PCV valve
3 - Ignition Coil
Fig. 39 Upstream Heated Oxygen Sensor 1/1
1 - OXYGEN SENSORS
2 - EXHAUST MANIFOLD
Fig. 40 Downstream Heated Oxygen Sensor 1/2
14 - 40
FUEL INJECTION
PT
MAP SENSOR (Continued)
deterioration, the fuel injection system uses two
heated oxygen sensors. One sensor upstream of the
catalytic convertor, one downstream of the convertor.
The PCM compares the reading from the sensors to
calculate the catalytic convertor oxygen storage
capacity and converter efficiency. Also, the PCM uses
the upstream heated oxygen sensor input when
adjusting injector pulse width.
When the catalytic converter efficiency drops below
emission standards, the PCM stores a diagnostic
trouble code and illuminates the malfunction indica-
tor lamp (MIL).
The O2 sensors produce a constant 2.5 volts on
NGC vehicles, depending upon the oxygen content of
the exhaust gas. When a large amount of oxygen is
present (caused by a lean air/fuel mixture, can be
caused by misfire and exhaust leaks), the sensors
produces a low voltage. When there is a lesser
amount of oxygen present (caused by a rich air/fuel
mixture, can be caused by internal engine problems)
it produces a higher voltage. By monitoring the oxy-
gen content and converting it to electrical voltage,
the sensors act as a rich-lean switch.
The oxygen sensors are equipped with a heating
element that keeps the sensors at proper operating
temperature during all operating modes. Maintaining
correct sensor temperature at all times allows the
system to enter into closed loop operation sooner.
Also, it allows the system to remain in closed loop
operation during periods of extended idle.
In Closed Loop operation the PCM monitors the O2
sensors input (along with other inputs) and adjusts
the injector pulse width accordingly. During Open
Loop operation the PCM ignores the O2 sensor input.
The PCM adjusts injector pulse width based on pre-
programmed (fixed) values and inputs from other
sensors.
NGC Controller - Has a common ground for the
heater in the O2S. 12 volts is supplied to the heater
in the O2S by the NGC controller. Both the upstream
and downstream O2 sensors for NGC are pulse width
modulation (PWM). NOTE: When replacing an O2
Sensor, the PCM RAM memory must be cleared,
either by disconnecting the PCM C-1 connector or
momentarily disconnecting the Battery negative ter-
minal. The NGC learns the characteristics of each O2
heater element and these old values should be
cleared when installing a new O2 sensor. The cus-
tomer may experience driveability issues if this is not
performed.
UPSTREAM OXYGEN SENSOR
The input from the upstream heated oxygen sensor
tells the PCM the oxygen content of the exhaust gas.
Based on this input, the PCM fine tunes the air-fuel
ratio by adjusting injector pulse width.
The sensor input switches from 2.5 to 3.5 volt,
depending upon the oxygen content of the exhaust
gas in the exhaust manifold. When a large amount of
oxygen is present (caused by a lean air-fuel mixture),
the sensor produces voltage as low as 2.5 volt. When
there is a lesser amount of oxygen present (rich air-
fuel mixture) the sensor produces a voltage as high
as 3.5 volt. By monitoring the oxygen content and
converting it to electrical voltage, the sensor acts as
a rich-lean switch.
The heating element in the sensor provides heat to
the sensor ceramic element. Heating the sensor
allows the system to enter into closed loop operation
sooner. Also, it allows the system to remain in closed
loop operation during periods of extended idle.
In Closed Loop, the PCM adjusts injector pulse
width based on the upstream heated oxygen sensor
input along with other inputs. In Open Loop, the
PCM adjusts injector pulse width based on prepro-
grammed (fixed) values and inputs from other sen-
sors.
DOWNSTREAM OXYGEN SENSOR
The downstream heated oxygen sensor input is
used to detect catalytic convertor deterioration. As
the convertor deteriorates, the input from the down-
stream sensor begins to match the upstream sensor
input except for a slight time delay. By comparing
the downstream heated oxygen sensor input to the
input from the upstream sensor, the PCM calculates
catalytic convertor efficiency. Also used to establish
the upstream O2 goal voltage (switching point).
Fig. 41 NGK O2 Sensors
PT
FUEL INJECTION
14 - 41
O2 SENSOR (Continued)
REMOVAL
REMOVAL - 1/1 UPSTREAM
(1) Remove the air cleaner lid and makeup air
hose.
(2) Remove the negative battery cable.
(3) Disconnect electrical connector from sensor.
(4) Remove sensor using an oxygen sensor special
tool C-4907 (Fig. 42).
REMOVAL - 1/2 DOWNSTREAM
The downstream heated oxygen sensor threads into
the exhaust pipe behind the catalytic convertor (Fig.
43).
(1) Remove the air cleaner lid and makeup air
hose.
(2) Remove the negative battery cable.
(3) Raise vehicle and support.
(4) Disconnect electrical connector from sensor.
(5) Disconnect sensor electrical harness from clips
along body.
(6) Remove sensor using an oxygen sensor crow
foot wrench such as Snap-On tool YA8875 or equiva-
lent (Fig. 44).
REMOVAL - 1/1 UPSTREAM - 1.6L
(1) Remove the air cleaner cover.
(2) Remove the negative battery cable.
(3) Disconnect electrical connector from O2 sensor.
(4) Remove sensor using an oxygen sensor crow
foot wrench such as Snap-On tool YA8875 or equiva-
lent (Fig. 45).
REMOVAL - 1/2 DOWNSTREAM - 1.6L
The downstream heated oxygen sensor threads into
the exhaust pipe behind the catalytic convertor (Fig.
46).
(1) Remove the air cleaner cover.
(2) Remove the negative battery cable.
(3) Raise vehicle and support.
(4) Disconnect electrical connector from sensor.
(5) Disconnect sensor electrical harness from clips
along body.
Fig. 42 Oxygen Sensor 1/1 Upstream
1 - DOWN STREAM O2 SENSOR
2 - UP STREAM O2 SENSOR
Fig. 43 Oxygen Sensor 1/2 Downstream
1 - DOWN STREAM O2 SENSOR
2 - UP STREAM O2 SENSOR
Fig. 44 Oxygen Sensor 1/2 Downstream
1 - DOWNSTREAM HEATED OXYGEN SENSOR
2 - CATALYTIC CONVERTOR
14 - 42
FUEL INJECTION
PT
O2 SENSOR (Continued)
(6) Remove sensor using an oxygen sensor crow
foot wrench such as Snap-On tool YA8875 or equiva-
lent (Fig. 47).
REMOVAL - 2.4L TURBO/2.4L SRT-4
(1) Disconnect the negative battery cable.
(2) Unlock and disconnect the electrical connector.
It is on the passenger side near the EVAP purge sole-
noid.
(3) Raise vehicle and support.
(4) Remove sensor (Fig. 48) using an oxygen sen-
sor crow foot wrench such as Snap-On tool YA8875 or
equivalent
INSTALLATION
INSTALLATION - 1/1 UPSTREAM
(1) After removing the sensor, the exhaust mani-
fold threads must be cleaned with an 18 mm X 1.5 +
6E tap. If reusing the original sensor, coat the sensor
threads with an anti-seize compound such as Loctite
t
771-64 or equivalent. New sensors have compound on
the threads and do not require an additional coating.
Tighten the sensor to 28 N·m (20 ft. lbs.) torque.
(2) Connect electrical connector to sensor.
(3) Install the negative battery cable.
(4) Install the air cleaner lid and makeup air hose.
Fig. 45 UPSTREAM O2 SENSOR 1/1
Fig. 46 DOWNSTREAM O2 SENSOR
Fig. 47 OXYGEN SENSOR REMOVAL TOOL
1 - DOWNSTREAM HEATED OXYGEN SENSOR
2 - CATALYTIC CONVERTOR
Fig. 48 UPSTREAM O2 SENSOR- 2.4L TURBO
PT
FUEL INJECTION
14 - 43
O2 SENSOR (Continued)
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