What it means
NOx Sensor Sensing Element Bank 1 Sensor 2: the control module has detected this fault condition.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 sensor 2 is the NOx sensor downstream of the SCR catalyst. Its sensing element measures the remaining NOx in the exhaust so the module can assess emissions treatment. This code indicates an internal sensing-element performance fault, which can make downstream NOx readings unreliable.
Common causes
Most likely first.
- Sensor element poisoned by silicone, sulphur or oil ash
- Thermal shock from condensate (cold start with wet exhaust)
- Sensor at end of service life
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 check for related NOx sensor heater, supply, wiring, or SCR codes.
- Confirm bank 1 sensor 2 from service information and inspect its connector and wiring for corrosion, heat damage, or loose pins.
- Review live downstream NOx data and compare it with upstream readings and engine operating conditions for an implausible or fixed signal.
- Inspect for an exhaust leak or signs of sensor contamination, including oil ash or soot deposits.
- If the circuit and exhaust checks pass, confirm the sensing-element fault using the manufacturer's procedure.
Common fixes
- Repair connector or wiring faults at bank 1 sensor 2.
- Repair an exhaust leak or correct an identified contamination source.
- Replace the bank 1 sensor 2 NOx sensor if the element fault is confirmed.
- Verify downstream NOx readings and emissions monitor operation after the repair.
Can I keep driving?
If the vehicle drives normally, use it gently and arrange repair soon because emissions monitoring may be inaccurate. Do not ignore AdBlue/DEF alerts or a restart countdown; some vehicles eventually restrict restarting.
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.