F 350 2WD Super Duty V10-6.8L (2009)
Oxygen Sensor: Description and Operation
Engine Control Components
Heated Oxygen Sensor (HO2S)
Engine Control Components
Heated Oxygen Sensor (HO2S)
The HO2S detects the presence of oxygen in the exhaust and produces a variable voltage according to the amount of oxygen detected. A high
concentration of oxygen (lean air/fuel ratio) in the exhaust produces a voltage signal less than 0.4 volt. A low concentration of oxygen (rich air/fuel ratio)
produces a voltage signal greater than 0.6 volt. The HO2S provides feedback to the PCM indicating air/fuel ratio in order to achieve a near
stoichiometric air/fuel ratio of 14.7:1 during closed loop engine operation. The HO2S generates a voltage between 0.0 and 1.1 volts.
Embedded with the sensing element is the HO2S heater. The heating element heats the sensor to a temperature of 800°C (1,472°F). At approximately
300°C (572°F) the engine can enter closed loop operation. The VPWR circuit supplies voltage to the heater. The PCM turns the heater on by providing
the ground when the correct conditions occur. The heater allows the engine to enter closed loop operation sooner. The use of this heater requires the
HO2S heater control to be duty cycled, to prevent damage to the heater.
Typical Heated Oxygen Sensor (HO2S)
Typical Heated Oxygen Sensor (HO2S)
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.
