OBD-II code · Powertrain (generic)
P0140 O2 Sensor Circuit No Activity / Slow Response (Bank 1 Sensor 2)
The ECU detects no switching or excessively slow response from the downstream oxygen sensor on bank 1. Typical for an aged or poisoned sensor; downstream sensors should show a relatively flat signal but must respond to fueling changes during diagnostic monitor runs.
Is it safe to drive with P0140?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelySensor aged or poisoned
- PossibleSensor heater circuit weak
- Less likelyCatalytic converter so degraded that downstream signal mirrors upstream
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Oxygen Sensor B1s2, Oxygen Sensor Heater Circuit, Catalytic Converter Bank1
Related codes
- P0134O2 Sensor Circuit No Activity / Slow Response (Bank 1 Sensor 1)
- P0146O2 Sensor Circuit No Activity / Slow Response (Bank 1 Sensor 3)
- P0154O2 Sensor Circuit No Activity / Slow Response (Bank 2 Sensor 1)
- P0160O2 Sensor Circuit No Activity / Slow Response (Bank 2 Sensor 2)
- P0166O2 Sensor Circuit No Activity / Slow Response (Bank 2 Sensor 3)
- P013DO2 Sensor Slow Response - Lean to Rich Bank 2 Sensor 2
- P013EO2 Sensor Delayed Response - Rich to Lean Bank 1 Sensor 2
- P013FO2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 2
- P0141O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
- P0142O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
- P0143O2 Sensor Circuit Malfunction (Bank 1 Sensor 3)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.