Powertrain, generic (extended)

P22A0 NOx Sensor Circuit Low (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Outlet NOx element drifted low or internally faulty
Engine software anomaly (GM 3.0L LZ0 2024, bulletin 24-NA-094)
Damaged lead between probe and sensor module

Symptoms

  • Malfunction indicator lamp on after two trips
  • Live data shows a negative downstream NOx value
  • SCR efficiency monitor does not complete

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

P229EP229FP22A1P22A2P2202

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