Diagnostic article Generic OBD-II
P22A1: NOx sensor 2 exceeds its upper reporting limit
P22A1 identifies an above-range post-catalyst NOx reading in the documented GM monitor.
Read before applying this article
Documented application
2025 GM 25OBDG04B diagnostic parameter file; the cited monitor is documented, but individual vehicle, engine and calibration applicability has not been established.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P22A1 is presented as the bank 1 sensor 2 NOx circuit-high monitor. Its strategy and enabling signals identify the post-catalyst sensor. The malfunction text contains a conflicting “NOx1” reference; this article follows the row heading and consistent NOx2 conditions, and does not use that isolated wording to change sensor identity.
High concentration versus electrical high
The actual threshold given is a raw NOx reading above 2,990 ppm. The monitor counts 360 failed samples out of 720 on a 25 ms task, with Type B, two-trip reporting. This makes the code a sustained upper-range assessment in this implementation, rather than a published voltage test.
Supply, dewpoint, valid CAN communication, internal current-control status and electrical health all qualify the result. The continuation also ties operation to air-system control or a ready, uninhibited reductant system.
Practical interpretation
First distinguish an above-range raw signal from an ordinary elevated NOx value that remains inside the sensor's range. Those observations do not invoke the same criterion. Then examine whether the conditions allowed this monitor to run, especially if other sensor or communication codes are present. An emissions-system efficiency conclusion cannot be made from this code alone. Confirm the exact vehicle's service information before selecting a sensor or applying a repair procedure.
Source and application limits
This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 1428. GM diagnostic parameters, PDF page 1429.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
NOx Sensor Circuit High Bank 1 Sensor 2
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT