P2AC5Intake Air O2 Sensor Reference Voltage Circuit Low Bank 2
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P2AC5 reports that the bank 2 intake oxygen sensor sees a reference voltage below the permitted limit, typically a short to ground in the reference lead or a breakdown of the sensing cell. No manufacturer publishes this code, and engines with a separate intake oxygen sensor for bank 2 are rare. If a vehicle does set it, compare with P2AC1: a fault on only one bank points to that sensor or its own harness branch, while both banks together hint at a shared ground, the sensor supply or the ECM. While the reference is pulled low, the bank 2 EGR feedback is lost and the ECM is expected to reduce recirculation, which raises NOx output but rarely affects driveability. CARB and Ford's sensor patents frame the check. P2AC6 is the high side, P2AC3 the open circuit.
- What you may notice
- Check engine light on
- Higher NOx, possibly a failed emissions test
- Likely causes
- LikelyReference wire of the bank 2 sensor shorted to ground
- PossibleSensing cell broken down internally
- RareShared sensor supply or ECM fault (if P2AC1 is present as well)
- 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.