P0166O2 Sensor Circuit No Activity Detected Bank 2 Sensor 3
- 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
- Sensor 3 on bank 2 is a switching oxygen sensor behind a second converter or converter brick. It is rare – documented for Jaguar Land Rover's supercharged V6 and V8 (2013–2016), where it is the 'post-cat' sensor of the second bank, and for Ford systems that monitor part of the converter volume. P0166 means sensor 3 shows no voltage change or stays in the control module's bias band – an open or high-resistance circuit, or a cold or dead sensor. For downstream sensor 2 GM sets the equivalent code when the voltage does not change after heater warm-up (within 15 s) or sits at 401–548 mV. No manufacturer document using exactly this code was found; Jaguar Land Rover does not list it and Ford uses only heater codes for sensor 3. A failed heater (P0167) can cause it. When it fails, the downstream evaluation of that converter is suspended; there is no limp mode.
- What you may notice
- Check engine light on (usually after two drive cycles)
- Often together with P0167
- Usually no noticeable change in driving
- Likely causes
- LikelySignal or ground wire open, connector corroded
- LikelySensor dead
- PossibleHeater failed (sensor stays cold)
- RareEngine control module
- 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 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.