P2203: NOx Sensor Circuit High Bank 1 Sensor 1
What to do
The car will drive normally, and the inducement countdown still runs. If any work has recently been carried out underneath the vehicle, ask for the sensor connector to be checked first — these get disturbed during exhaust and suspension jobs, and a plug not fully seated gives exactly this code.
What this code means
The NOx sensor circuit reads above its valid range — an open circuit, a short to supply, or a reported concentration beyond what the module will accept as real.
As with the low variant, the ambiguity between an electrical fault and a genuine reading matters, and here it matters more: a very high NOx figure is what a completely failed reduction system produces. The distinction the module draws is one of plausibility — a figure above what any engine could physically emit is electrical; a figure that is merely far too high is the range/performance code at P2201 and is quite possibly true.
An open circuit is also what a disconnected sensor looks like. These connectors are underneath the vehicle and are routinely disturbed by exhaust work, suspension work or anything involving a ramp, so a code appearing shortly after other work under the car deserves a physical check before any testing.
Likely causes
Start here
- Open circuit in sensor wiring · moderate
- Disconnected sensor connector · easy
- Faulty NOx sensor · moderate
- Corroded or loose connector · easy
Less common
- Wiring shorted to voltage · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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