P2A00O2 Sensor Circuit Range/Performance Bank 1 Sensor 1
- 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 1 on bank 1 is the oxygen sensor ahead of the catalytic converter that the engine control module relies on for mixture feedback. P2A00 is a plausibility fault: a signal is present but does not behave the way fuel control expects. GM petrol engines (LCV, LEA, LHN) set it when the sensor never becomes ready for closed-loop fuelling or falls out of it again, counted as 200 failed samples out of 250 and logged as a two-trip Type B fault; on Saab's 9-4X with GM V6 engines 30 s with the fuel loop still open are enough. Ford's 2023 diesels compare the measured oxygen share with a value derived from injected quantity, boost pressure and exhaust gas recirculation and expect close to 20.95 % in overrun. On GM's 3.0 L diesel a leaking intake manifold triggered it (bulletin 22-NA-128).
- What you may notice
- Check engine light on
- Engine runs in open loop, fuel consumption rises
- Uneven idle or hesitation
- Failed emissions inspection
- Likely causes
- LikelySensor aged or poisoned (oil ash, silicone, coolant), signal too weak or sluggish
- PossibleLeak in intake manifold or exhaust ahead of the sensor distorts the oxygen reading
- PossibleHigh resistance or corrosion in signal, reference or heater wiring
- RareFuel delivery or injector fault the sensor correctly reports but fuel control cannot correct
- 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 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.