P0140 Code: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
🟢 Low severity · drivable
Safe to drive — this downstream sensor only monitors the catalytic converter.
What P0140 means
The bank 1 downstream oxygen sensor is producing no signal at all. It's dead, unplugged, or its wiring is open. Since this sensor only monitors the catalytic converter, the main consequence is a failed emissions test rather than a drivability issue.
Symptoms
- Check engine light on
- Usually no driving symptoms
Common causes
- most common: Faulty downstream oxygen sensor (dead)
- 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 or connector | Mechanic | $50–150 |
Frequently asked questions
What's the difference between P0140 and P0136?
P0136 is a general circuit fault; P0140 means the downstream sensor is producing no signal at all.
What causes P0140?
A dead downstream oxygen sensor, or broken wiring to it.
How much does it cost to fix P0140?
Typically $60–$200 for a 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)
Related guide: MAF Sensor Replacement Cost →
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.