Crossfire V6-3.2L VIN L (2004)
The O2 sensors produce voltages from 0 to 1 volt, 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 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.
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 preprogrammed (fixed) values and inputs
from other sensors.
The engine control relay located in the relay control module supplies battery voltage to both the upstream and downstream heated oxygen sensors. The
oxygen sensors are equipped with a heating element. The heating elements reduce the time required for the sensors to reach operating temperature. The
PCM uses pulse width modulation to control the ground side of the heater to regulate the temperature.
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 output varies from 0 to 1 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 0.1 volt. When there is a lesser amount of oxygen present
(rich air-fuel mixture) the sensor produces a voltage as high as 1.0 volt. By monitoring the oxygen content in the exhaust gases and comparing that to the
oxygen content in ambient air 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 signals. In Open Loop, the
PCM adjusts injector pulse width based on preprogrammed (fixed) values and inputs from other sensors.
DOWNSTREAM OXYGEN SENSOR
The downstream heated oxygen sensor signal is used to detect catalytic convertor deterioration. As the convertor deteriorates, the signal from the
downstream sensor begins to match the upstream sensor signal except for a slight time delay. By comparing the downstream heated oxygen sensor signal
to the signal from the upstream sensor, the PCM calculates catalytic convertor efficiency. This calculation is also used to establish the upstream O2 goal
voltage (switching point).
