Powertrain
generic / SAE
P0138
O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
The downstream oxygen sensor signal is fixed at a high voltage, indicating either a continuously rich downstream reading (less common, since post-cat exhaust should be more stable) or a short to supply voltage in the signal circuit.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number1 / 38
Possible causes
- Signal wire shorted to supply voltage high
- Downstream sensor failed medium
- Connector pins corroded - high contact resistance low
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Inspection / repair
- Difficulty: easy
- DIY: possible
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References
sae:J2012