P23AE: 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. 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.

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 after two trips
Negative or zero NOx value for sensor 3 in live data
Other harness-related codes stored at the same time

Most likely causes

Engine harness chafed, disturbing the sensor 3 supply or signal
Sensor 3 with a negative offset from ageing or damage
Water in the sensor connector

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes and the NOx data before and after the SCR catalyst
With the connector unplugged, check whether the signal wire is making contact with ground.
Check the sensor's connector and wiring
Look for exhaust leaks ahead of the sensor
Confirm that the AdBlue/DEF is of good quality
Replace the sensor only after ruling out power, ground, and leaks

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P23AE means

P: Powertrain: engine and transmission
2: Generic code: same on every make
3: Ignition and misfires
AE: Specific fault in that system

Frequently asked questions

Can I keep driving with code P23AE?

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 P23AE?

The most common causes are: engine harness chafed, disturbing the sensor 3 supply or signal; sensor 3 with a negative offset from ageing or damage; water in the sensor connector.

Related codes

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.