Ranger 2WD V6-182 3.0L (1995)
OPERATION
The zirconium dioxide in the sensor is electrically sensitive to differences in the amount of oxygen present between two sources. The outside of
the sensor is vented to the atmosphere while the inside is exposed to the exhaust stream. The differing amounts of oxygen present between the two
sources causes the sensor to generate a voltage.
A rich fuel mixture will result in a low level of oxygen present in the exhaust. This will produce a larger difference in oxygen levels sensed by
the HO2S which will result in a higher voltage being produced.
A lean fuel mixture will result in a high level of oxygen present in the exhaust. This will produce a smaller difference in oxygen levels sensed
by the HO2S which will result in a lower voltage being produced.
Normal operating range for the HO2S is 0.0 volts (lean condition) to 1.1 volts (rich condition).
The HO2S temperature must be above 600°F to operate properly. To minimize heat up time, a heating element is incorporated into the sensor.
HEATED OXYGEN SENSOR #2 or CATALYST MONITOR SENSOR (downstream)
PURPOSE
The Heated Exhaust Gas Oxygen Sensor #2
(HO2S) indicates catalyst efficiency based on oxygen storage capacity.
OPERATION
Closed loop fuel control is transferred from upstream to downstream HO2S. The switching frequency of the downstream HO2S output is
measured. This actual measured output frequency is called the test frequency. The test frequency is an indication of the oxygen storage capacity of
the catalytic converter. The oxygen storage capacity of a high efficiency will have a low switch ration and high HC efficiencies. As catalyst
efficiency deteriorates, its ability to store oxygen declines and it will begin to have a higher switch ratio and low HC efficiencies.
