Concorde V6-2.7L VIN V (2001)
Fig. 22 Downstream Heated Oxygen Sensor 1/2, 2/1
The downstream heated oxygen sensor threads into the outlet pipe at the rear of the catalytic convertor.
Separate controlled ground circuits are run through the PCM for the upstream O2 sensors.
As vehicles accumulate mileage, the catalytic convertor 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
indicator lamp (MIL).
The O2S produce voltages 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 sensors produces a low voltage. When there is a lesser amount present (rich air/fuel mixture) 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 O2S 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 Automatic Shutdown (ASD) relay 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.
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, 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 airfuel mixture) the sensor produces a voltage as high as 1.0 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 preprogrammed (fixed) values and inputs from other sensors.
