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Chevrolet Cavalier exhaust Oxygen Sensor information FYI

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  • Chevrolet Cavalier exhaust Oxygen Sensor information FYI

    Document ID# 690395
    2001 Chevrolet Cavalier (CNG)
    ________________________________________
    DTC P0171

    Circuit Description
    The exhaust Oxygen Sensor (O2S) is used in order to determine the oxygen content of the engine's exhaust. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the engine is operating lean the exhaust will have more oxygen content. Once at operating temperature, the O2S will produce a voltage in relation to the oxygen content of the exhaust. The O2S requires an operating temperature of 360°C (600°F) to produce voltage. The O2S will produce more voltage when the exhaust is rich and less voltage when the exhaust is lean. The O2S operating voltage range is around 0.10 volts (100 mV) to 1 volt (1000 mV).
    The AF ECU utilizes a Closed Loop air/fuel metering system when the O2S is at operating temperature. During normal Closed Loop fuel control operation the AF ECU will add fuel (enriches the mixture) when the O2S indicates a lean exhaust content. When the O2S indicates a rich exhaust content the AF ECU will subtract fuel (leans-out the mixture). This addition and subtraction to the air/fuel mixture may be indicated on a scan tool as the Long and Short Term Fuel Trim values. Short Term Fuel Trim values are adjustments to the fuel mixture that occur quickly. Long Term Fuel Trim values are adjustments to the fuel mixture that accumulate over longer periods of time. The Long and Short Term Fuel Trim values are displayed on a scan tool as a percent. Positive percentage values indicate fuel is being added to the mixture. Negative percentage values indicate fuel is being subtracted from the mixture.
    This DTC is used to indicate a fully rich fuel trim system that cannot compensate for a lean engine exhaust content.
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