What it means
The bank 1 sensor 2 NOx sensor circuit signal is above the expected range. The code does not by itself establish an open circuit or identify the failed component.
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 downstream NOx sensor, whose circuit reports exhaust NOx readings to the control module. This code sets when the circuit signal rises above the expected range; it does not by itself establish an open circuit or prove that the sensor has failed.
Common causes
Most likely first.
- Open signal line
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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
- Check freeze-frame data and related NOx codes to identify when the bank 1 sensor 2 signal went high.
- Inspect the downstream sensor harness for pinched insulation, contact with a B+ source, heat damage, or chafing.
- Check connector pins for corrosion, loose fit, or damage that could interrupt the signal path.
- Use scan-tool data to see whether the signal stays high under different operating conditions.
- Test the signal and supply circuits for an open, short to power, or excessive resistance according to the wiring diagram and manufacturer's specification.
Common fixes
- Repair a signal wire shorted to a power source.
- Repair an open or damaged section of the harness.
- Restore proper connector pin contact and repair corrosion.
- Replace bank 1 sensor 2 if it fails testing after the circuit is verified.
Can I keep driving?
You can generally drive cautiously if the engine runs normally, but the NOx system may not control or monitor emissions correctly. Repair it promptly, since a DEF warning or later start countdown may follow.
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.