Voyager L4-2.4L VIN B (2001)
Oxygen Sensor: Description and Operation
Fig. 17 O2 Sensor Upstream 1/1
The upstream oxygen sensor threads into the outlet flange of the exhaust manifold.
Fig. 19 O2 Sensor Downstream 1/2
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).
