Content .. 546 547 548 549 ..

Chrysler Sebring, Stratus sedan, Sebring Convertible. Manual - part 548

The PCM uses the MAP sensor to aid in calculat-

ing the following:

• Barometric pressure

• Engine load

• Manifold pressure

• Injector pulse-width

• Spark-advance programs

• Idle speed

• Decel fuel shutoff
The MAP sensor signal is provided from a single

piezoresistive element located in the center of a dia-
phragm. The element and diaphragm are both made
of silicone. As the pressures changes the diaphragm
moves causing the element to deflect which stresses
the silicone. When silicone is exposed to stress its
resistance changes. As manifold vacuum increases,
the MAP sensor input voltage decreases proportion-
ally. The sensor also contains electronics that condi-
tion

the

signal

and

provide

temperature

compensation.

The PCM recognizes a decrease in manifold pres-

sure by monitoring a decrease in voltage from the
reading stored in the barometric pressure memory
cell. The MAP sensor is a linear sensor; as pressure
changes, voltage changes proportionately. The range
of voltage output from the sensor is usually between
4.5 volts at sea level to as low as 0.3 volts at 26 in. of
Hg. Barometric pressure is the pressure exerted by
the atmosphere upon an object. At sea level on a
standard day, no storm, barometric pressure is 29.92
in Hg. For every 100 feet of altitude barometric pres-
sure drops .10 in. Hg. If a storm goes through it can
either add, high pressure, or decrease, low pressure,
from what should be present for that altitude.You
should make a habit of knowing what the average
pressure and corresponding barometric pressure is
for your area. Always use the Diagnostic Test Proce-
dures Manual for MAP sensor testing.

REMOVAL

REMOVAL - 4 CYLINDER

(1) Disconnect the negative battery cable.
(2) Disconnect electrical connector from MAP sen-

sor (Fig. 21).

(3) Remove two screws holding sensor to the

intake manifold.

REMOVAL - 2.7L

(1) Remove the negative battery cable.
(2) Disconnect the electrical connector from the

MAP sensor (Fig. 22).

(3) Remove bolt from sensor.
(4) Remove sensor.

INSTALLATION

INSTALLATION - 4 CYLINDER

(1) Install sensor.
(2) Install two screws and tighten.
(3) Connect the electrical connector to the MAP

sensor (Fig. 21).

(4) Connect the negative battery cable.

Fig. 21 GENERATOR AND MAP SENSOR

1 - Generator
2 - MAP Sensor

Fig. 22 MAP SENSOR - 2.7L

FUEL INJECTION

14 - 29

MAP SENSOR (Continued)

INSTALLATION - 2.7L

(1) The sensor mounts onto intake manifold ple-

num (Fig. 23). Tighten screws to 4.5 N·m (40 in. lbs.)
torque.

(2) Attach electrical connector to sensor (Fig. 22).
(3) Install the negative battery cable.

O2 SENSOR

DESCRIPTION

The upstream oxygen sensor threads into the out-

let flange of the exhaust manifold (Fig. 24) or (Fig.
25).

The downstream heated oxygen sensor threads into

the outlet pipe at the rear of the catalytic convertor
(Fig. 26).

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
deterioration, the fuel injection system uses two

Fig. 23 MAP SENSOR O-RING

Fig. 24 O2 SENSOR UPSTREAM 1/1 4 CYLINDER

Fig. 25 O2 SENSORS 2.7L

1 - Upstream 2/1
2 - Upstream 1/1
3 - Downstream 1/2
4 - Downstream 2/2

Fig. 26 O2 SENSOR DOWNSTREAM 2/1 4

CYLINDER

14 - 30

FUEL INJECTION

MAP SENSOR (Continued)

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).

REMOVAL

REMOVAL - DOWNSTREAM 1/2 4 CYLINDER

The O2S is located in the side of the catalytic con-

verter (Fig. 26).

WARNING: THE EXHAUST MANIFOLD, EXHAUST
PIPES

AND

CATALYTIC

CONVERTER

BECOME

VERY HOT DURING ENGINE OPERATION. ALLOW
ENGINE TO COOL BEFORE REMOVING OXYGEN
SENSOR.

(1) Remove the negative battery cable.
(2) Raise and support the vehicle.
(3) Disconnect the wire connector from the O2S.

CAUTION: When disconnecting the sensor electrical
connector, do not pull directly on wire going into
sensor.

(4) Remove

the

O2S.

Snap-On

oxygen

sensor

wrench (number YA 8875) may be used for removal
and installation.

FUEL INJECTION

14 - 31

O2 SENSOR (Continued)

REMOVAL - Downstream 1/2, 2/2 2.7L

The O2S are located at the outlet ends of the cat-

alytic converter (Fig. 25).

WARNING: THE EXHAUST MANIFOLD, EXHAUST
PIPES

AND

CATALYTIC

CONVERTER

BECOME

VERY HOT DURING ENGINE OPERATION. ALLOW
ENGINE TO COOL BEFORE REMOVING OXYGEN
SENSOR.

(1) Remove the negative battery cable.
(2) Raise and support the vehicle.
(3) Disconnect the wire connector from the O2S.

CAUTION: When disconnecting the sensor electrical
connector, do not pull directly on wire going into
sensor.

(4) Remove

the

O2S.

Snap-On

oxygen

sensor

wrench (number YA 8875) may be used for removal
and installation.

REMOVAL - Upstream 1/1, 2/1 2.7L

The engines uses two heated oxygen sensors, one

in each exhaust manifold (Fig. 25).

CAUTION: When disconnecting the sensor electrical
connector, do not pull directly on wire going into
sensor.

(1) Remove the negative battery cable.
(2) Remove the air cleaner box for the rear O2 sen-

sor.

(3) Disconnect the heated oxygen sensor electrical

connector.

(4) Use a Special tool #8439 to remove oxygen sen-

sor.

REMOVAL - UPSTREAM 1/1 4 CYLINDER

The engine uses 1 heated oxygen sensors in the

exhaust manifold.

CAUTION: When disconnecting the sensor electrical
connector, do not pull directly on wire going into
sensor.

(1) Remove the negative battery cable.
(2) Disconnect the heated oxygen sensor electrical

connector.

(3) Use a socket such as Snap-On YA8875 or a

crow foot wrench to remove oxygen sensor (Fig. 25).

INSTALLATION

INSTALLATION - DOWNSTREAM 1/2 4
CYLINDER

The O2S are located in the side of the catalytic

converter (Fig. 26).

(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
771- 64 or equivalent. New sensors have compound
on the threads and do not require an additional coat-
ing.

(2) Install the O2S. Tighten to 28 N·m (20 ft. lbs.)

torque.

(3) Connect the O2S wire connector.
(4) Lower the vehicle.
(5) Install the negative battery cable.

INSTALLATION - Downstream 1/2, 2/2 2.7L

The O2S are located at the outlet ends of the cat-

alytic converter (Fig. 25).

(1) After removing the sensor, the exhaust mani-

(2) Install the O2S. Tighten to 28 N·m (20 ft. lbs.)

torque.

(3) Connect the O2S wire connector.
(4) Lower the vehicle.
(5) Install the negative battery cable.

INSTALLATION - Upstream 1/1, 2/1 2.7L

The engines uses two heated oxygen sensors, one

in each exhaust manifold (Fig. 25).

(1) After removing the sensor, the exhaust mani-

(2) Use a Special tool #8439 to install oxygen sen-

sor. Tighten the sensor to 28 N·m (20 ft. lbs.) torque.

(3) Connect the heated oxygen sensor electrical

connector.

(4) Install the air cleaner box.
(5) Install the negative battery cable.

14 - 32

FUEL INJECTION

O2 SENSOR (Continued)

Content .. 546 547 548 549 ..