Second air error on scan tool
#11
You'll need a scanner that is capable of graphing the oxygen sensors individually to spot a problem. The monitor relies heavily on oxygen sensor data. Oxygen sensors react to changes in fuel mixture. Reaction time from lean to rich, and rich to lean can vary, even on brand new sensors. The faster they react to changes, the faster the PCM can correct the mixture to achieve the best possible fuel mileage. As they age, thier reaction time slows down, (normal). When it gets too slow in one or both directions, the PCM sets a DTC in memory. The "failure" point is programmed into the PCM software, and can vary between model years. If one or both upstream oxygen sensors are close to the "failure" point, it might affect the secondary air monitor.
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Mikeinnh
2nd Generation S-series (1995-2005) Tech
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