P0140O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The oxygen sensor after the catalytic converter on bank 1 (sensor 2) is a switching sensor (about 0.1–0.9 V) used for converter monitoring and fine mixture trim. P0140 means the sensor produces no voltage of its own and the control module only sees its own reference (bias) voltage. GM's V6 sets it when the signal sits at 401–548 mV or the sensor's internal resistance exceeds 40 kΩ when it should be hot; newer GM systems apply 1900 mV and read above 1700 mV as an open circuit. Two trips. Ford reports 'no activity' under P0136 instead. A cold sensor with a failed heater can also cause it. When it fails, the control module stops the downstream trim and cannot evaluate the converter; there is no limp mode.
- What you may notice
- Check engine light on (usually after two drive cycles)
- Catalyst monitor readiness not set
- Live data: sensor 2 stuck at about 450 mV (or 1.9 V)
- Likely causes
- LikelySignal or ground wire open, connector off or corroded
- PossibleSensor heater failed, sensor never becomes active
- PossibleSensor worn out (no longer produces voltage)
- RareControl module input faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €50 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.