Powertrain, generic (extended)

P2203 NOx Sensor Circuit High (Bank 1 Sensor 1)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Upstream NOx sensor reading high due to internal failure
ECM software anomaly (GM 3.0L LZ0, bulletins 23-NA-193 and 24-NA-094)
Sensing element contaminated by oil ash or DEF deposits

Symptoms

  • Malfunction indicator lamp on
  • Implausibly high upstream NOx value in live data
  • Possible over-dosing of AdBlue or SCR efficiency codes

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–1,000
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

nox sensornox sensor wiring

Related codes

P2200P2201P2202P2204P22A1P2216

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.