Powertrain, generic (extended)

P22A6 NOx Sensor Heater Sense Circuit (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Besides the heater supply, a NOx sensor has a sense line through which its module measures the resistance of the heated element and so infers its temperature. P22A6 reports an electrical fault on that feedback line of the rear sensor on bank 1. GM's 3.0L LZ0 sets it for an open circuit at the HTemp pin, 80 failures in 160 samples, Type A after one trip; GM notes that the Continental Gen 3.5 sensor debounces electrical faults internally for 1.5 s. The 2017 small diesels use the same open-circuit check with 20 failures in 40 samples, also Type A. Volvo and Mack list P22A6 among codes that call for a new outlet sensor; GM bulletin 24-NA-094 names it Heater Feedback Circuit and covers it with an LZ0 software update. P22A8/P22A9 are shorts, P22A7 plausibility, P2208 the front sensor.

Likely causes

Open heater sense conductor inside the outlet NOx probe or its lead
Water or corrosion in the probe connector
Software anomaly (GM 3.0L LZ0 2024, bulletin 24-NA-094)

Symptoms

  • Malfunction indicator lamp on after one trip
  • Outlet NOx sensor not ready, no downstream value
  • 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

P22A7P22A8P22A9P22AAP22A3P2208

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