P2A10O2 Sensor Negative Voltage 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 downstream oxygen sensor of bank 2, behind that bank's converter, is reporting a negative voltage. Bank 2 only exists on V and flat engines. A healthy switching sensor swings between roughly 0.1 and 0.9 V; readings below zero come from swapped signal and return wires, for instance after splicing in a universal sensor, from a fouled reference air path or from a cracked ceramic. No manufacturer documents P2A10 publicly. Ford monitors precisely this condition on rear sensors with a limit of −0.2 V held over 10 s but stores P2A04 for bank 2. A Denso patent treats negative readings during fuel cut-off as a sign of an element crack. The engine itself runs normally, but converter monitoring on bank 2 is blocked until the cause is fixed.
- What you may notice
- Check engine light on
- Catalyst monitor of bank 2 not ready
- No change in driving behaviour
- Likely causes
- LikelySignal and return wires swapped, e.g. on a spliced universal sensor
- PossibleCracked ceramic of the bank 2 downstream sensor
- RareReference air path fouled
- 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: €50 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.