P0140moderate severityPowertrain
O2 Sensor Circuit No Activity Bank 1 Sensor 2
on 2004 Subaru Legacy 3.0L H6 · AWD
What this code means
The downstream O2 sensor on Bank 1 shows no switching activity.
Symptoms
- Check Engine Light
- No catalyst monitoring
Common causes
- Faulty sensor
- Heater circuit failure
- Wiring open
Diagnostic steps
- Test sensor voltage
- Check heater
- Inspect wiring
Repair notes
Replace downstream O2 sensor.
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P0002
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P0010
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P0014
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P0015
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