Powertrain, generic (extended)

P2221 NOx Sensor Heater Sense Circuit (Bank 2)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Alongside the heater drive, a NOx sensor has a sense path that tells the electronics how the heater is really behaving, usually by measuring its resistance, which tracks cell temperature. P2221 reports a general fault in that sense circuit on the bank 2 sensor. Public documentation exists only for the bank 1 code P2208: GM's 3.0L LZ0 checks the separate HTemp pin for an open load, 80 failures in 160 samples at over 11 V, Type A with the MIL after one trip, and notes that its Continental sensors debounce electrical faults internally for 1.5 s. No manufacturer lists the bank 2 version. Without valid feedback the sensor cannot regulate its temperature. P2222 to P2225 are the specific sense faults.

Likely causes

Fault in the heater measurement of the bank 2 sensor
Open sense conductor between probe and sensor module
Corrosion in the sensor connector

Symptoms

  • Malfunction indicator lamp on
  • Bank 2 NOx sensor not ready

Repair estimate

DifficultyMediumWorkshop job
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 heaternox sensor wiring

Related codes

P2208P2218P2222P2223P2224P2225

References: law.cornell.edu, gsi.ext.gm.com, ni.com.