Circuit Description
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VCM supplies a voltage of about .45 volt between HO2S signal and HO2S ground circuits. HO2S varies voltage from about one volt with rich exhaust to 0.1 volt with lean exhaust. HO2S produces no voltage and acts as an open circuit when temperature is less than 600°F (316°C). An open sensor circuit or a cold sensor causes open loop operation.
HO2S heater provides for faster sensor warm-up allowing sensor to become active in a shorter period of time and remain active during long extended idle. DTC test determines if HO2S heater is operating properly by monitoring amount of time necessary for HO2S to become active after start-up.