P237AO2 Sensor Exhaust Sample Error (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
- P237A says the rear oxygen sensor of bank 1 is not getting, or not reporting, a representative sample of exhaust: its reading does not fit the gas that should be flowing past it after the catalyst, typically because outside air enters through a leak or the sensing element is no longer exposed properly. No manufacturer documents P237A publicly. Volkswagen describes the front-sensor counterpart P2414 for the 2014 Golf with signal windows of 3.10 to 4.81 V and 2.5 to 3.2 V, which gives an idea of how such a plausibility check is built. CARB requires rear sensors to be monitored for faults that would spoil their use in catalyst and fuel control monitoring. P2414/P2415 cover sensor 1; code lists repeat this title under P23A0. Drivability is normally unaffected, but catalyst diagnosis becomes unreliable.
- What you may notice
- Check engine light on
- Catalyst monitor not completing or reporting implausible results
- Possible ticking exhaust noise from a leak
- Likely causes
- LikelyLeak at a flange, joint or cracked pipe ahead of the bank 1 rear sensor drawing in air
- PossibleRear sensor element damaged, coated or loose in its boss
- RareContaminated or blocked reference air path of the sensor (wiring or connector)
- 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: €20 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.