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.
Medium severity. Can I keep driving?You can usually keep driving in the short term, but get it repaired soon: on many diesels, the warning eventually limits starting or engine power.
Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.
Symptoms
- Check engine light
- SCR efficiency or NOx plausibility codes may follow
Most 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
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P224A means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 2: Fuel injection
- 4A: Specific fault in that system
Frequently asked questions
Can I keep driving with code P224A?
You can usually keep driving in the short term, but get it repaired soon: on many diesels, the warning eventually limits starting or engine power.
What causes code P224A?
The most common causes are: heating element of the NOx sensor aged or cracked; corroded or loose contacts in the sensor connector; unstable supply voltage to the sensor module.
Related codes
- P224BNOx Sensor Heater Resistance (Bank 1 Sensor 2)
- P2209NOx Sensor Heater Sense Circuit Range/Performance (Bank 1 Sensor 1)
- P2205NOx Sensor Heater Control Circuit/Open (Bank 1 Sensor 1)
- P0053HO2S Heater Resistance Bank 1 Sensor 1
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.