Removal - Upstream 1/1 Or 2/1; Removal - Downstream 1/2 Or 2/2 - Chrysler 300M Service Manual

LH
O2 SENSOR (Continued)
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 0 to 1 volt, depend-
ing upon the oxygen content of the exhaust gas in
the exhaust manifold (this is offset by 2.5 voltage on
NGC vehicles). When a large amount of oxygen is
present (caused by a lean air-fuel mixture), the sen-
sor produces voltage as low as 0.1 volt. When there is
a lesser amount of oxygen present (rich air-fuel mix-
ture) the sensor produces a voltage as high as 1.0
volt. By monitoring the oxygen content and convert-
ing 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 - UPSTREAM 1/1 or 2/1

The engines uses two heated oxygen sensors, one
in each 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. 21).
Fig. 21 Upstream Heated Oxygen Sensor 1/1
1 - PROPORTIONAL PURGE SOLENOID
2 - O2 SENSOR

REMOVAL - DOWNSTREAM 1/2 or 2/2

The O2 sensors are located at the outlet ends of
the catalytic converter (Fig. 22).
Fig. 22 Downstream Heated Oxygen Sensors—1/2
(R) 2/2 (L)
1 - OXYGEN SENSORS
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.
FUEL INJECTION 14 - 31