What it means
The bank 1 sensor 2 NOx sensor circuit signal is below the expected range. The code does not by itself establish a short to ground 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, and its signal circuit carries readings to the control module. This code sets when that circuit's signal falls below the expected range; it does not by itself prove a short to ground or identify the failed part.
Common causes
Most likely first.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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
- Review freeze-frame data and related NOx codes to confirm when the bank 1 sensor 2 signal went low.
- Inspect the downstream sensor connector and harness for chafing, exposed conductors, corrosion, or moisture.
- Check connector pin fit and look for contamination or corrosion that could increase contact resistance.
- Use scan-tool data to monitor the sensor signal and see whether it remains low as exhaust conditions change.
- Test the signal, supply, and ground circuits for shorts and excessive resistance using the wiring diagram and manufacturer's specification.
Common fixes
- Repair chafed wiring or a shorted signal conductor.
- Clean or repair corroded connector terminals and restore proper pin contact.
- Replace bank 1 sensor 2 if it fails circuit testing after wiring faults are ruled out.
Can I keep driving?
Cautious driving is generally possible if the vehicle runs normally, but emissions control may be impaired and a NOx or DEF warning may appear. Address it promptly because some vehicles can begin a start countdown after the fault is ignored.
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.