P2203NOx Sensor Circuit High (Bank 1 Sensor 1)
- 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
- P2203 flags a raw NOx value from the upstream sensor on bank 1 that lies above anything the engine can actually emit. The limits differ: GM sets 1,500 or 2,500 ppm on the 6.6L Duramax (LML) and 2,500 ppm on the 3.0L LZ0 (Type B, two trips), VW 1,655 ppm on the 2014 Touareg TDI. On 2023 and 2024 Silverado and Sierra 1500 pickups with the LZ0, GM bulletins 23-NA-193 and 24-NA-094 trace the code to software and prescribe an ECM update. Volvo and Mack class P2203 on the inlet sensor as a likely sensor failure and replace that sensor alone. P2202 is the lower limit, P2201 a plausible-looking but wrong reading, P22A1 the downstream counterpart. The MIL is on; SCR control loses a reliable input.
- What you may notice
- Malfunction indicator lamp on
- Implausibly high upstream NOx value in live data
- Possible over-dosing of AdBlue or SCR efficiency codes
- Likely causes
- LikelyUpstream NOx sensor reading high due to internal failure
- PossibleECM software anomaly (GM 3.0L LZ0, bulletins 23-NA-193 and 24-NA-094)
- RareSensing element contaminated by oil ash or DEF deposits
- 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.