DTC P0138 or P0158 is also set if the heated oxygen sensor voltage output is more than 1.2 V for 10 seconds or more.
*: The three-way catalytic converter has the capability to store oxygen. The oxygen storage capacity and the emission purification
capacity of the three-way catalytic converter are mutually related. The ECM determines whether the catalyst has deteriorated,
based on the calculated oxygen storage capacity value See: P0420.
4. High or Low Impedance of Heated Oxygen Sensor (DTCs P0136 and P0156 or P0137 and P0157)
During normal air fuel ratio feedback control, there are small variations in the exhaust gas oxygen concentration. In order to continuously
monitor the slight variation of the heated oxygen sensor signal while the engine is running, the impedance* of the sensor is measured by the
ECM. The ECM determines that there is a malfunction in the sensor when the measured impedance deviates from the standard range.
*: The effective resistance in an alternating current electrical circuit.
HINT
- The impedance cannot be measured using an ohmmeter.
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