P0140: Downstream O2 sensor circuit no activity (Bank 1 Sensor 2)
You can keep driving. Get it checked when convenient.
Can I drive with P0140?
Yes, you can keep driving. Downstream sensor unplugged or dead; engine management is not impaired.
What does P0140 mean?
P0140 stands for O2 Sensor Circuit No Activity Detected (Bank 1, Sensor 2).
Symptoms you may notice
- Check engine light on with no noticeable change in how the car drives
- Vehicle fails state emissions smog test
- Normal engine power and shifting
How much does it cost to fix?
Repair costs for code P0140 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:
- Disconnected underbody sensor connector
- Severed sensor wiring harness from road hazard
- Dead downstream oxygen sensor
- Severe corrosion in undercarriage connector
What to do next
- Inspect the wiring connector underneath the front passenger compartment.
- Check that the connector is latched and the wiring harness is secured.
- Replace the downstream sensor if the circuit is intact.
Last updated: October 2026
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General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.
About this code
Code P0140 means the powertrain computer sees no activity on Bank 1 Sensor 2. Because this sensor is located beneath the vehicle, its wires are frequently snagged by road debris or unplugged during transmission or exhaust repairs and forgotten. The car is safe to drive.