P0159O2 Sensor Circuit Slow Response Bank 2 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 2 (sensor 2) is a switching sensor (about 0.1–0.9 V) used for converter monitoring and fine mixture trim. Bank 2 exists only on V and boxer engines with a separate downstream sensor per bank. P0159 means the downstream sensor on bank 2 reacts too slowly to mixture changes, typically measured around fuel cut-off. Thresholds are documented only for the bank 1 counterpart P0139 (Subaru: 0.51 s rich to lean, 2 s lean to rich); Jaguar Land Rover lists P0159 for its mid-cat sensor after water-induced thermal shock. Newer GM and Ford systems report direction-specific codes P013C/P013D and P014A/P014B instead. 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
- P0430 may follow
- Likely causes
- LikelySensor aged or contaminated (oil ash, silicone, additives)
- PossibleExhaust leak ahead of the sensor
- PossibleSensor heater weak, sensor too cold
- RareThermal shock damage from water
- 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: €60 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.