P2A05O2 Sensor Circuit Range/Performance 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
- P2A05 refers to the third oxygen sensor on bank 2, mounted behind a further converter or aftertreatment stage of a V or flat engine. No manufacturer documents this code publicly. The nearest documented case is its bank-1 counterpart: GM's 2025 diesel tables compare the oxygen value of sensor 3 with that of sensor 2 at full load and set P2A02 when the gap exceeds 6 % in 120 of 240 samples. Ford's downstream checks show the other route into a range fault, a reading that sinks below −0.2 V, which Ford, however, files only for sensor 2. CARB requires downstream sensors to stay good enough for the monitors that rely on them. An implausible sensor 3 goes largely unnoticed while driving, but the converter or aftertreatment check of bank 2 cannot finish.
- What you may notice
- Check engine light on
- Readiness for the catalyst or aftertreatment monitor missing
- Usually no change in driving behaviour
- Likely causes
- LikelyThird sensor on bank 2 drifting or slow with age
- PossibleExhaust leak in the pipe between sensor 2 and sensor 3
- RareDamaged or heat-affected wiring under the vehicle
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €80 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.