All engines run on an optimum
fuel to air mixture called "stokiometric" which means chemically balanced. This
balanced fuel to air ratio is 14.7 to 1, 14.7 parts air to 1 part fuel. The
oxygen sensor is created using
the active chemical such as zirconium, electrochemical (also known as Galvanic),
infrared, ultrasonic and very recently laser. When a lean mixture code is detected
by you or a technician the first tendency is to
replace the oxygen sensor.
The best way to check the operation of the sensor is to run a simple test. No matter
if your engines oxygen sensor has one wire or four there is only one sensing wire
that feedbacks information to the computer (PCM). To find this wire you will need
a car repair manual.
If a trouble code is present that pertains to
an oxygen heater sensor failure, replace the sensor to repair the problem. An oxygen
sensor must be warm before it will operate properly.
Note: If a malfunction exists with related components such as an engine misfire
or engine vacuum leak do not perform this test. The oxygen sensor is designed to
operate within a particular range, if this range is exceeded the sensor will give
the appearance that it has failed.
Oxygen Sensor - (appearances will vary)
Oxygen Sensor Test
Tools needed to perform these tests: Voltmeter
Step 1 - Once the oxygen sensor sensing wire has been located
connect a volt meter to the feedback wire and ground. Select the millivolt operation
on the voltmeter.
Step 2 - Next, start and run the engine at idle until warm (about
15 minutes). Observe the voltmeter; it should bounce slightly at whatever voltage
the sensor is centered at (about 150 millivolts).
Step 3 - Continue to observe the meter and have a helper rap
the throttle. The meter should drop for a split second as the mixture leans out
in the first milliseconds of the throttle bore being opened. Then quickly rise for
a spit second as the throttle closes and the mixture richens. The volt meter should
stabilize at the original operating voltage when the engine returns to idle.
If further assistance is needed, our certified car repair technicians are ready
to answer your car questions.
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