Escape 2WD L4-2.5L Hybrid (2010)
Oxygen Sensor: Description and Operation
Universal Heated Oxygen Sensor (HO2S)
ENGINE CONTROL COMPONENTS
Universal Heated Oxygen Sensor (HO2S)
The universal HO2S, sometimes referred to as a wideband oxygen sensor, uses the typical HO2S combined with a current controller in the PCM to
infer an air/fuel ratio relative to the stoichiometric air/fuel ratio. This is accomplished by balancing. the amount of oxygen ions pumped in or out of a
measurement chamber within the sensor. The typical HO2S within the universal HO2S is used to detect the oxygen content of the exhaust gas in the
measurement chamber. The oxygen content inside the measurement chamber is maintained at the stoichiometric air/fuel ratio by pumping oxygen ions
in and out of the measurement chamber. As the exhaust gasses get richer or leaner, the amount of oxygen that must be pumped in or out to maintain a
stoichiometric air/fuel ratio in the measurement chamber varies in proportion to the air/fuel ratio. The amount of current required to pump the oxygen
ions in or out of the measurement chamber is used to measure the air/fuel ratio. The measured air/fuel ratio is actually the output from the current
controller in the PCM and not a signal that comes directly from the sensor.
The universal HO2S also uses a self-contained reference chamber to make sure an oxygen differential is always present. The oxygen for the reference
chamber is supplied by pumping small amounts of oxygen ions from the measurement chamber into the reference chamber. The universal HO2S does
not need access to outside air.
Part to part variance is compensated for by placing a resistor in the connector. This resistor is used to trim the current measured by the current
controller in the PCM.
Embedded with the sensing element is the universal HO2S heater. The heater allows the engine to enter closed loop operation sooner. The heating
element heats the sensor to a temperature of 780°C (1,436°F). The VPWR circuit supplies voltage to the heater. The PCM controls the heater on and
off by providing the ground to maintain the sensor at the correct temperature for maximum accuracy.
