P22A0NOx Sensor Circuit Low (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
- P22A0 reports that the rear NOx sensor on bank 1 sends a raw value below the smallest figure a healthy sensor can produce. Because the sensor talks over CAN, the test looks at the transmitted number rather than a wire voltage. GM uses minus 90 ppm on the 6.6L LML, on its 2017 small diesels (table 17OBDG04) and on the 3.0L LZ0, in each case Type B after two trips with dew point reached and supply in range; the LZ0 needs 100 failed samples in 200. VW's 2014 Touareg TDI faults below minus 105 ppm or a lambda signal under minus 0.2. GM bulletin 24-NA-094 puts P22A0 on the list cured by an LZ0 software update on 2024 Silverado and Sierra 1500. A strongly negative value usually means element drift or an internal fault. P22A1 is the upper limit, P2202 the front sensor.
- What you may notice
- Malfunction indicator lamp on after two trips
- Live data shows a negative downstream NOx value
- SCR efficiency monitor does not complete
- Likely causes
- LikelyOutlet NOx element drifted low or internally faulty
- PossibleEngine software anomaly (GM 3.0L LZ0 2024, bulletin 24-NA-094)
- RareDamaged lead between probe and sensor module
- 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.