P2203
NOx Sensor Circuit High Bank 1 Sensor 1
Emissions / NOx sensor
Generic OBD-II
Medium
What it means
P2203 means the ECM read an abnormally high signal from the number-one NOx sensor on bank 1. This sensor measures nitrogen-oxide levels for the emissions (and, on diesels, SCR) system. The engine runs normally, but the emissions monitoring is compromised, so the fault usually points to the sensor, its wiring, or connector.
Medium
Can I keep driving? The engine runs normally, but the emissions/SCR system relies on this sensor; leaving it can trigger warning lights, failed emissions, and eventually a power derate on some diesels.
Common symptoms
What you'll notice
- Check-engine light on
- Possible emissions / SCR warning messages
- Higher tailpipe NOx (may fail an emissions test)
- On some diesels, eventual power derate if ignored
Common causes
Most likely first
- Faulty NOx sensor (bank 1, sensor 1)Likely
- Open or shorted NOx sensor wiring pushing the signal highCommon
- Poor or corroded connector at the sensorCommon
- Contaminated sensor tip or an exhaust leak near the sensorLess often
How to diagnose & fix
Work through it in order
- Scan the NOx sensor live data and compare against a known-good range.
- Inspect the sensor connector and wiring for damage, shorts, or corrosion.
- Check for exhaust leaks near the sensor that could skew readings.
- Replace the NOx sensor if its output stays high with good wiring.
- Clear and complete a drive cycle to confirm.
FAQ
Quick answers
Is it safe to drive with P2203?+
Mechanically yes, but this is an emissions sensor — expect the light to stay on, possible emissions-test failure, and on some diesels a gradual power derate if it's ignored.
Can I just clear P2203?+
It returns while the sensor or wiring is faulty, and the emissions system stays flagged until it's repaired.
Related codes
Often seen with P2203
Read & clear P2203 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX