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Testing Sensors
Section
2
Location
The sensor is threaded into the exhaust manifold to
give it direct contact with the exhaust gases.
How it is
used?
The computer uses this sensor to calculate
optimum air/fuel mixture for low emissions and
good fuel economy. If the sensor indicates a rich
exhaust (not enough oxygen because of too much
fuel), the computer will compensate by reducing
fuel delivery. If the computer receives a lean signal
(too much oxygen because of too little fuel), it will
increase fuel delivery. NOTE: Some vehicles use
more than one oxygen sensor.
What is It? The oxygen sensor is a zirconium dioxide ceramic
mounted in the tip of a threaded metal housing.
The tip is perforated to protect the sensing element
but still allow exhaust gases to pass through.
The sensor produces a voltage signal based on the
amount of oxygen it contacts. A low voltage
indicates a lean exhaust (too much oxygen). A
higher voltage signals a rich exhaust (not enough
oxygen).
The sensor must be very hot to operate: 349(C
(660(F). Many have 2-wire heating elements built-
in to quicken the warm-up time.
Typical Oxygen Sensor