P0140 Code: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
🟢 Low severity · drivable
Safe to drive — this downstream sensor fault mainly affects emissions monitoring.
What P0140 means
The bank 1 downstream oxygen sensor is producing no usable signal at all. It monitors the catalytic converter, so this is an emissions concern.
Symptoms
- Check engine light is on
- Usually no driving symptoms
Common causes
- most common: Faulty downstream oxygen sensor
- common: Open or damaged sensor wiring
- less common: Loose or corroded sensor connector
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the bank 1 downstream oxygen sensor | Yes | $60–200 |
| Repair open sensor wiring | Mechanic | $50–150 |
Frequently asked questions
Can I drive with a P0140 code?
Yes. It mainly affects emissions monitoring, not drivability.
What is the most common cause of P0140?
A faulty downstream oxygen sensor.
How much does it cost to fix a P0140?
Typically $60–$200 for a new downstream oxygen sensor.
Related codes
P0136
P0136 Code: O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0134P0134 Code: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
P0141P0141 Code: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.