P224ANOx Sensor Heater Resistance (Bank 1 Sensor 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- Check engine light
- SCR efficiency or NOx plausibility codes may follow
- Likely causes
- LikelyHeating element of the NOx sensor aged or cracked
- PossibleCorroded or loose contacts in the sensor connector
- RareUnstable supply voltage to the sensor module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €250 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.