Chrysler 2000 LHS - Downstream Heated Oxygen Sensor; Heated Oxygen Sensor (O2 Sensor); Upstream Heated Oxygen Sensor

HEATED OXYGEN SENSOR (O2 SENSOR)—
PCM INPUT
DESCRIPTION
The upstream oxygen sensor threads into the out-
let flange of the exhaust manifold (Fig. 4) or (Fig. 5).
The downstream heated oxygen sensor threads into
the outlet pipe at the rear of the catalytic convertor
(Fig. 6).
OPERATION
Separate controlled ground circuits are run
through the PCM for the upstream O2 sensors.
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
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 O2S produce voltages from 0 to 1 volt, depend-
ing upon the oxygen content of the exhaust gas in
the exhaust manifold. When a large amount of oxy-
gen is present (caused by a lean air/fuel mixture), the
sensors produces a low voltage. When there is a
lesser amount present (rich air/fuel mixture) it pro-
duces a higher voltage. By monitoring the oxygen
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.
Fig. 4 Upstream Heated Oxygen Sensor 1/1
1 – O2 SENSOR
Fig. 5 Upstream Heated Oxygen Sensor 1/1
1– PROPORTIONAL PURGE SOLENOID
2– O2 SENSOR
Fig. 6 Downstream Heated Oxygen Sensor 1/2
1 – OXYGEN SENSORS
LH FUEL SYSTEM 14 - 29
DESCRIPTION AND OPERATION (Continued)