P22AFO2 Sensor Reference Voltage Performance (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
- P22AF is a plausibility fault on the Nernst-cell (reference voltage) side of the bank 1 downstream wide-band probe: the wiring is intact, but the cell signal does not behave as the controller expects, for instance it cannot be held at its set point or drifts. Typical reasons are an aged cell whose resistance has risen above the roughly 300 ohms Bosch quotes for the LSU 4.9, soot or oil deposits, or a heater that keeps the element too cool. No maker documents this code publicly. CARB requires the OBD system to catch deterioration of voltage, impedance, current or offset of air-fuel sensors behind the aftertreatment before emissions rise too far. Siblings: P22AE open, P22B0/P22B1 low/high, P22BC bank 2, P2244 upstream.
- What you may notice
- Check engine light
- Downstream oxygen reading sluggish or offset compared with the upstream sensor
- Catalyst or aftertreatment monitor may report errors as a follow-up
- Likely causes
- LikelyAged downstream wide-band sensor with raised cell resistance
- PossibleSoot, oil or coolant deposits on the sensing element
- RareWeak heater or heater control that leaves the element too cold
- RareHigh-resistance contact in the Nernst-cell circuit
- 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 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.