The heated oxygen sensor 1 is placed into the exhaust manifold. Itdetects the amount of oxygen in the exhaust gas compared to theoutside air. The heated oxygen sensor 1 has a closed-end tubemade of ceramic zirconia. The zirconia generates voltage fromapproximately 1V in richer conditions to 0V in leaner conditions. Theheated oxygen sensor 1 signal is sent to the ECM. The ECM adjuststhe injection pulse duration to achieve the ideal air-fuel ratio. Theideal air-fuel ratio occurs near the radical change from 1V to 0V.
DTC DETECTION LOGIC Under the condition in which the heated oxygen sensor 1 signal is not input, the ECM circuits will read a continuous approximately0.3V. Therefore, for this diagnosis, the time that output voltage iswithin 200 to 400 mV range is monitored, and the diagnosis checksthat this time is not inordinately long.