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 (manifold) 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 DETECTING CONDITION CHART
| DTC No. | Trouble diagnosis name | 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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