Powertrain, generic (extended)

P22AA NOx Sensor Heater Sense Circuit Intermittent (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P22AA covers a heater sense line on the rear NOx sensor of bank 1 that fails only now and then. The module uses this line to read the element temperature and keep the heater on target; if the reading drops out or jumps for short moments, the temperature control briefly loses its reference and the sensor may fall out of its ready state. No manufacturer publicly documents a threshold or a bulletin for P22AA, and GM, Ford and VW do not list it in their published tables. CARB asks for continuous monitoring of NOx sensor heater circuits, and smart sensors report the heater circuit state (open, short, no error) over CAN. In practice, check terminal grip, cable routing near hot parts and water ingress. P22A6, P22A8 and P22A9 are the steady faults, P2212 the front sensor.

Likely causes

Loose or corroded terminal in the probe connector
Lead near the exhaust cracked by heat or vibration
Intermittent internal contact fault in the probe

Symptoms

  • Malfunction indicator lamp that may come and go
  • Outlet NOx sensor intermittently not ready

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–900
Time0.5–3 h

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

Parts involved

nox sensornox sensor heaternox sensor wiring

Related codes

P22A6P22A7P22A8P22A9P2212

References: law.cornell.edu, ni.com, hella.com.