P22A1NOx Sensor Circuit High (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
- P22A1 flags a raw value from the rear NOx sensor on bank 1 that is higher than anything plausibly left behind the SCR catalyst. GM's 6.6L LML uses 1,500 ppm, or 2,500 ppm in table 14OBDG10; the 3.0L LZ0 and the 2017 small diesels also use 2,500 ppm, Type B after two trips. VW's 2014 Touareg TDI uses 1,655 ppm or a lambda signal above 1.54. Volvo and Mack count P22A1 among codes that point to a damaged outlet sensor and replace that sensor alone. For Ram ProMaster vans, a 2025 Stellantis case (S2525000001) reports P22A1 together with P20EE, asks for standard diagnosis including the DEF condition and states that engineering is still looking for the root cause. GM includes the code in LZ0 software bulletin 24-NA-094. P22A0 is the lower limit, P2203 the front sensor.
- What you may notice
- Malfunction indicator lamp on
- Implausibly high downstream NOx value in live data
- SCR efficiency code P20EE stored alongside
- Likely causes
- LikelyOutlet NOx sensor reading high due to internal damage
- PossibleDEF quality or dosing problem raising real tailpipe NOx
- RareEngine software anomaly (GM 3.0L LZ0 2024, bulletin 24-NA-094)
- 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 – €1,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.