DTC Detection Logic
The heated oxygen sensor 2 has a much longer switching time between rich and lean than the air fuel ratio (A/F) sensor 1. The oxygen storage capacity of the three way catalyst 1 causes the longer switching time.
MALFUNCTION A
To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the voltage is unusually high during various driving conditions such as fuel cut.
MALFUNCTION B
To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the minimum voltage of sensor is sufficiently low during various driving conditions such as fuel cut.
| DTC No. | Trouble diagnosis content | DTC detecting condition | Possible cause | |
|---|---|---|---|---|
| P0138 | Heated oxygen sensor 2 circuit high voltage | A) | An excessively high voltage from the sensor is sent to ECM. |
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| B) | The minimum voltage from the sensor is not reached to the specified voltage. |
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