P23AE code meaning
NOx Sensor Circuit Low (Bank 1 Sensor 3)
Powertrain system Generic code P23xx codes Check engine light
What P23AE means
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.
P23AE at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P23AE
- 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
Common causes of P23AE
- Most likelyEngine harness chafed, disturbing the sensor 3 supply or signal
- PossibleSensor 3 with a negative offset from ageing or damage
- Less likelyWater in the sensor connector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensor b1s3
What each part of P23AE means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 3 | Area: ignition system or misfire. |
| AE | The exact fault in that area. |
What to do next
- Note P23AE and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P23AE
What does P23AE mean?
P23AE means "NOx Sensor Circuit Low (Bank 1 Sensor 3)". P23AE is set when the third NOx sensor on bank 1 reports a concentration below anything physically possible. It is a generic code, so it means the same on every make.
Is it safe to drive with P23AE?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P23AE fail an emissions test?
Yes, it can. P23AE is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P23AE to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P23AE clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.