What it means
The bank 1 NOx sensor circuit signal is above the expected range. This circuit code does not by itself identify the sensor failure mode or wiring fault.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The bank 1 NOx sensor circuit sends exhaust nitrogen oxide information to the control module. P2203 sets when the circuit signal is above its expected range, which points to a high-signal condition rather than the low-signal fault indicated by a different code.
Common causes
Most likely first.
- Signal wire shorted to supply
- Sensor failed high
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Record related codes and freeze-frame data to see when the bank 1 circuit went high and whether a shared supply fault is present.
- Inspect the bank 1 NOx sensor connector and harness for rubbed-through insulation, heat damage, corrosion, or a signal wire touching a supply wire.
- Use the wiring diagram to test for a short to supply and verify circuit continuity, sensor power, ground, and connector terminal condition.
- If wiring and feeds meet the manufacturer’s specification, test the bank 1 sensor signal to determine whether the high reading originates inside the sensor.
Common fixes
- Repair a bank 1 NOx signal wire shorted to supply.
- Repair damaged harness insulation or connector terminals causing the high signal.
- Correct a confirmed sensor power or ground fault.
- Replace the bank 1 NOx sensor if its output remains high with the circuit verified.
Can I keep driving?
If the vehicle drives normally, keep trips limited while arranging diagnosis because emissions control may not work correctly. Respond promptly to any DEF warning or restart countdown.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.