P2AC4Intake Air O2 Sensor Reference Voltage Circuit Range/Performance Bank 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
- P2AC4 marks an implausible but electrically intact reference voltage on the second-bank intake oxygen sensor. It is the bank 2 twin of P2AC0, which Stellantis documents for the four-cylinder Alfa Romeo 2.0L; an inline four with one intake path has no bank 2, so P2AC4 would only appear on engines fitted with a second intake sensor. No manufacturer documents this code publicly. A plausibility test of this kind typically compares the sensor reading with what EGR valve position, intake pressure and air mass lead the ECM to expect; Ford's patents show that pressure changes and humidity shift the output and must be compensated. Ageing, contamination from crankcase vapours or an overly strict calibration are therefore likelier causes than a broken wire. P2AC3 is the open circuit.
- What you may notice
- Check engine light on
- Usually no noticeable change in driveability
- Likely causes
- LikelyBank 2 intake oxygen sensor aged or contaminated by crankcase vapours
- PossibleCalibration that judges the signal too strictly
- RareHigh resistance in the reference wire or connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €0 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.