P0140: O2 Sensor Circuit No Activity Detected — Bank 1 Sensor 2
What to do
No driveability impact. Have the connector inspected before the sensor is replaced — corrosion is the leading cause on this position.
What this code means
The downstream bank 1 sensor signal is flat. An open circuit is the most common cause, and on an underfloor sensor that frequently means a connector corroded until its pins no longer meet, or a wire severed by road debris. Check for an accompanying heater code, since a sensor that never warms will never produce a signal either.
Likely causes
Start here
- Open circuit in sensor wiring · moderate
- Corroded or loose connector · easy
- Faulty oxygen sensor · easy
Less common
- Failed oxygen sensor heater element · easy
- Road damage to underfloor wiring · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P0140.