ENGINE CONTROL SYSTEM 3-11
Zirconia element
Housing
O
2
SENSOR (Optional item)
The O
2
sensor is installed in the exhaust manifold only when the
O
2
feedback operation is performed.
This sensor is a zirconia element (platinum plated) which changes
output voltage depending on the oxygen concentration difference
between its internal and external surface. The voltage change
reflects the concentration of the oxygen in the exhaust gas and
is used to perform the O
2
feedback operation.
The terminal voltage change (0 – 1 V) is dependent on the con-
centration of oxygen in the exhaust gas.
This detected voltage value therefore represents the oxygen con-
centration. The terminal voltage decreases when the oxygen con-
centration is high, and increases when it is low.
NOTE:
As the zirconia element is not conductive below 250°C, the O
2
sensor will not function properly until the engine is at normal
operating temperature.
NOTE:
Zirconia element
The zirconia element produces a potential difference (voltage)
when there is a difference in the oxygen concentration of the
gases which contact the two sides of the element.
Since the inner surface of the zirconia element (inside the sen-
sor) is exposed to atmospheric air and the outer surface exposed
to the exhaust gas, there is a difference in oxygen concentration
on each side and thus a difference in the potential generated.
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