P23A1O2 Sensor Exhaust Sample Error (Bank 2 Sensor 2) - Duplicate Listing of P237B
- 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
- P23A1 is listed with the same title as P237B: the bank 2 oxygen sensor behind the catalyst reports something that cannot be genuine exhaust from that bank. Only engines with two exhaust banks and a downstream sensor on each side could produce it. No published OBD summary or bulletin assigns P23A1, and no source gives it its own meaning; it is thus a duplicate listing of P237B, itself without public manufacturer use. A comparable plausibility check is documented only for a front sensor, Volkswagen's P2414 on the 2014 Golf. Should the code appear, the manufacturer's definition takes precedence; practical checks cover air leaks on the bank 2 pipe, sensor position and wiring. CARB demands that rear sensors are monitored because catalyst diagnosis depends on them.
- What you may notice
- MIL on, engine runs normally
- Readiness for catalyst monitor stays open
- Likely causes
- LikelyScan tool reporting the duplicate number
- PossibleLeak in the bank 2 exhaust pipe ahead of the rear sensor
- RareDamaged wiring or connector of the bank 2 rear sensor
- 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: €0 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.