P0140
Low SeverityO2 Sensor Circuit No Activity (Bank 1, Sensor 2)
Emissions System
What Does P0140 Mean?
The downstream O2 sensor on bank 1 shows no voltage changes at all. The sensor is likely dead.
Common Fix
Replace downstream O2 sensor
Estimated Cost (DIY)
$25 - $80
Symptoms
- ⚠️Check engine light
- ⚠️Failed emissions test
Common Causes
Dead O2 sensorlikely
Disconnected sensorpossible
Heater failure preventing warm-uppossible
How to Diagnose P0140
- 1Verify sensor is connected
- 2Check heater circuit
- 3Monitor voltage — flat line confirms dead sensor
- 4Replace sensor
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Frequently Asked Questions
- Is P0140 urgent?
- Not at all for driveability. The downstream sensor does not affect engine performance. But it will fail emissions.
- Can I just clear P0140?
- You can clear it, but it will return if the sensor is dead. Replace the sensor for a permanent fix.