Powertrain, generic (extended)

P22A4 NOx Sensor Heater Control Circuit Low (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P22A4 means the heater control line of the rear NOx sensor on bank 1 has a short to ground, so the sensor module can no longer drive the heater as commanded. GM documents it on the 3.0L LZ0 as a ground short on the heater control pin, judged once dew point is reached and sensor supply exceeds 9.9 V, 80 failures in 160 samples, Type B after two trips. Its 2017 small diesels watch the H+ supply pin of the Gen 3.0 sensor instead, 20 failures in 40 samples. Volvo and Mack count P22A4 among codes that indicate a damaged outlet sensor, and GM bulletin 24-NA-094 adds it to an LZ0 software update for 2024 Silverado and Sierra 1500. Expect the MIL after two trips and no downstream NOx data. P22A3 is the open circuit, P22A5 a short to voltage, P2206 the front sensor.

Likely causes

Heater element or probe lead shorted to ground inside the sensor
Probe lead insulation chafed against the exhaust or body
Software anomaly (GM 3.0L LZ0 2024, bulletin 24-NA-094)

Symptoms

  • Malfunction indicator lamp on after two trips
  • Outlet NOx sensor stays not ready
  • SCR warning on the display

Repair estimate

DifficultyMediumDIY possible
Parts and labour€150–1,000
Time0.5–2.5 h

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

Parts involved

nox sensornox sensor heater

Related codes

P22A3P22A5P22A6P2206

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