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.
- DTC P0136 or P0156 indicates the deterioration of the heated oxygen sensor. The ECM sets the DTCs by calculating the
impedance of the sensor when the typical enabling conditions are satisfied (2 driving cycles).
- DTC P0137 or P0157 indicates an open or short circuit in the heated oxygen sensor (2 driving cycles). The ECM sets the DTCs
when the impedance of the sensor exceeds the threshold 15 kOhms.
5. Heated Oxygen Sensor Voltage Fuel Cut (DTC P0139 and P0159)
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