Fault criteria, front heated oxygen sensor
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Fault criteria, front heated oxygen sensor
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The oxygen sensor's ability to react quickly to changes in the fuel-air
mixture is diagnosed once per trip. The sensor's transition frequency is measured when
the conditions for diagnosis are fulfilled. Transition is what happens when the sensor voltage
goes from high to low or from low to high. If the transition frequency is too low, the sensor is
defective.
The number of sensor transitions taking place during 265 engine revolutions is counted.
If the number exceeds 12 the diagnosis is OK. If the number of transitions is less than 12, two
additional attempts to obtain a "diagnosis OK" result this trip will be made. If the sensor is
failed on all three diagnostic occasions the fault criteria are satisfied.
In other respects the sensor and its heating element are monitored according to the On-
Board Diagnostic I model.
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Diagnosis not yet performed this
trip
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Coolant temperature above 60°C
(140°F)
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Sensor heating current less than 1500 mA
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1.
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Count:
-number of sensor transitions
-number of engine revolutions
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2.
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> 12 sensor transitions during 265 engine revolutions
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3.
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Function monitored this trip
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4.
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Fault criteria for oxygen sensor 1 transition-diagnose fulfilled
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5.
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Third attempt to pass test
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6.
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Next event enable criteria are fulfilled during this
trip
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