Powertrain, generic (extended)

P22A1 NOx Sensor Circuit High (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Outlet NOx sensor reading high due to internal damage
DEF quality or dosing problem raising real tailpipe NOx
Engine software anomaly (GM 3.0L LZ0 2024, bulletin 24-NA-094)

Symptoms

  • Malfunction indicator lamp on
  • Implausibly high downstream NOx value in live data
  • SCR efficiency code P20EE stored alongside

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

P229EP229FP22A0P22A2P2203P20EE

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