Description: Located in the exhaust
system at one or more points, an oxygen sensor converts the status
of the engine's air/fuel mixture into a corresponding voltage
signal. The oxygen sensor is sometimes referred to as a Lambda
sensor on some European cars. The most common type of sensor uses a
zirconia element to generate voltage. Titania oxygen sensors, on the
other hand, use the technology of electrical resistance to produce
similar voltage characteristics as zirconia sensors. Regardless of
the technology used, changes in the air/fuel mixture result in a
voltage change that is monitored by the vehicle's powertrain control
module. Many oxygen sensors also have built-in heaters, to warm them
to operating temperature more quickly. Prior to 1996, most cars
had one
oxygen sensor. In 1996, Onboard Diagnostics II (OBDII) became standard technology for all
makes and models. OBD II systems use one oxygen
sensor on the inlet to the catalytic converter and another one on the outlet. On cars with dual converters, there may be as many as four oxygen sensors.
Purpose: The oxygen sensor reports
live information about the engine's air/fuel mixture to the
powertrain control module. This information is used primarily to
help calculate fuel delivery to the engine, which changes
continuously while it is running. If the engine is running lean, the
powertrain control module will sense this from the oxygen sensor's
signal and increase the air/fuel mixture
to the engine. Conversely, just the opposite occurs
when the engine begins to run rich. On OBDII-equipped vehicles,
the sensors are also
used to
help determine the efficiency of the catalytic converter.
The powertrain control module does this by comparing the signal
of the sensor located at the inlet of the catalytic converter
with the signal of the sensor located at the outlet of
the converter.
Maintenance Tips/Suggestions: Replace at the interval as recommended in
the owner's manual or when other conditions dictate, such as failing
an emissions test. Some cars have an oxygen sensor light that
appears when oxygen sensor replacement is needed. Some symptoms of a
faulty oxygen sensor include poor gas mileage, a failed emissions
test, "rotten-eggs" smell from the exhaust, poor acceleration and
more. Although a faulty oxygen sensor can cause
the SERVICE ENGINE SOON or CHECK ENGINE light to appear, it's
best to have the cause checked out immediately by a professional
technician. This is especially true if the SERVICE ENGINE SOON or
CHECK ENGINE light flashes rather than staying
on steady. Neglecting these warning signs can cause expensive damage
to the catalytic converter, requiring replacement.
