Powertrain, generic (extended)

P224A NOx Sensor Heater Resistance (Bank 1 Sensor 1)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P224A concerns the heater of the upstream NOx sensor on bank 1, the one before the SCR catalyst. Its electrical resistance rises with temperature, so the sensor electronics use it to hold the ceramic element at working heat. The code says that resistance is outside its allowed band, pointing to an aged or damaged element or a contact problem. No maker documents P224A publicly. GM performs the same test on the 3.0 L LZ0 Duramax (2025) but reports it as P2209: the measured resistance may differ from the target by no more than 3 %, judged on 50 of 100 readings once the supply has been above 10.8 V for 45 s and the dew point was passed 180 s earlier, Type B. A sensor with this fault reads NOx unreliably; P224B is the downstream sensor.

Likely causes

Heating element of the NOx sensor aged or cracked
Corroded or loose contacts in the sensor connector
Unstable supply voltage to the sensor module

Symptoms

  • Check engine light
  • SCR efficiency or NOx plausibility codes may follow

Repair estimate

DifficultyMediumDIY possible
Parts and labour€250–900
Time0.5–1.5 h

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

Parts involved

nox sensornox sensor heater

Related codes

P224BP2209P2205P0053

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