What it means
The NOx sensor on bank 1 sensor 2 reads suspiciously high for too long — biased upward or stuck. Common after sensor poisoning by silicon, sulphur, or oil ash.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The NOx sensor at bank 1, sensor 2 measures nitrogen oxides downstream in the exhaust for emissions-system monitoring. P225E sets when its reading remains higher than expected or fails to change normally; contamination or an aged sensor element can cause this high-biased signal.
Common causes
Most likely first.
- Sensor poisoned
- Sensor element aged beyond calibration window
- Sensor element contaminated by oil, soot or coolant
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 freeze-frame data and graph the bank 1 sensor 2 NOx signal across operating conditions to see whether it stays high.
- Inspect the downstream sensor connector and harness for exhaust heat damage, corrosion, and poor pin contact.
- Check for exhaust leaks and related engine faults that could produce genuinely high NOx readings.
- Look for evidence of oil, coolant, soot, or other deposits that could contaminate the sensor element.
- If the high signal persists after circuit and engine checks, test bank 1 sensor 2 against the manufacturer's specification.
Common fixes
- Repair damaged wiring or connector contact at bank 1 sensor 2.
- Repair exhaust leaks or engine faults contributing to high NOx readings.
- Correct any confirmed oil or coolant contamination source.
- Replace bank 1 sensor 2 if its signal remains high-biased after related faults are addressed.
Can I keep driving?
Driving is often possible, but emissions failure and NOx or DEF warnings may follow, with a possible no-start countdown on some vehicles. Do not defer repair if a countdown appears.
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.