P23AENOx Sensor Circuit Low (Bank 1 Sensor 3)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P23AE is set when the third NOx sensor on bank 1 reports a concentration below anything physically possible. GM's 25OBDG04B table for its 2025 diesels requires the raw NOx value of the sensor behind the second catalyst to fall under −90 ppm in 100 of 200 samples, taken every 25 ms once dew point is reached, supply exceeds 9.9 V and no CAN fault is present; it is rated Type B with the MIL after two trips. GM bulletin 21-NA-149 lists P23AE among the codes caused by chafed engine harnesses on 3.0L LM2 Duramax pickups and SUVs of 2021–2022 (Silverado and Sierra 1500, Tahoe, Suburban, Yukon, Escalade). CARB demands out-of-range checks on NOx sensors. P23AF is the high limit, P2202 and P22A0 are the low codes of sensors 1 and 2.
- What you may notice
- Check engine light after two trips
- Negative or zero NOx value for sensor 3 in live data
- Other harness-related codes stored at the same time
- Likely causes
- LikelyEngine harness chafed, disturbing the sensor 3 supply or signal
- PossibleSensor 3 with a negative offset from ageing or damage
- RareWater in the sensor connector
- 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: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.