Engine Petrol Engines
Rear HO2S
• A zirconium element is used on the sensor. When there is a difference between the
oxygen concentration inside and outside the element, electromotive force is generated
by the movement of oxygen ions (inside of the zirconium element: atmosphere, outside:
exhaust gas). The electromotive force changes significantly at the boundary of the
stoichiometric air/fuel ratio (= 14.7). The PCM receives the voltage generated from the
HO2S directly, and increases or decreases the fuel injection amount by the fuel injection
control so that it is close to the stoichiometric air/fuel ratio.
• When the temperature of the zirconium element is low, electromotive force is not
generated. Therefore the HO2S is heated by a built-in heater, facilitating the oxygen
sensor activation. Due to this, the sensor is efficiently activated even immediately after
cold-engine startup, and a stable sensor output can be obtained.
M6FL_01022
1 High 4 Rich
2 Output voltage 5 Air/fuel ratio
3 Low 6 Lean
Service Training Mazda6 Facelift 01-25
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