Circuit Description
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PCM monitors Heated Oxygen Sensor (HO2S) activity for 100 seconds. During this period, PCM counts number of times that HO2S switches from rich-to-lean and lean-to-rich. When PCM determines that HO2S does not switch enough times, DTC will set.
A lean-to-rich switch is determined when HO2S voltages changes from less than 300 mV to greater than 600 mV. A rich-to-lean switch is determined when HO2S voltage changes greater than 600 mV to less than 300 mV. DTC will set when PCM determines that within 100 seconds, the HO2S lean-to-rich and rich-to-lean switches are less than 10.