What it means
A fault has been detected in the sensing element of the NOx sensor on Bank 1 Sensor 3.
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 3 measures nitrogen oxides in the exhaust so the control module can check aftertreatment performance. This code sets when the module detects a fault in that sensor’s sensing element, which can prevent it from reporting exhaust NOx accurately.
Common causes
Most likely first.
- NOx sensor sensing element degraded or damaged
- Sensor element contaminated by exhaust deposits
- Electrical connection or wiring fault at the sensor
- Internal NOx sensor fault
Symptoms
- Check engine light
- Possible NOx or aftertreatment warning
- Increased NOx emissions or failed emissions test
How to diagnose it
- Read stored and pending codes and freeze-frame data to see when the Bank 1 Sensor 3 fault occurred and whether related aftertreatment codes are present.
- Use live data to compare the Bank 1 Sensor 3 NOx reading with other available exhaust data under the same operating conditions.
- Inspect the Bank 1 Sensor 3 body and exhaust area for damage, leaks, or deposits that could contaminate the sensing element.
- Check the sensor connector and harness for corrosion, loose pins, heat damage, or chafing near the exhaust.
- Test the sensor power, ground, and signal circuits against the manufacturer's specification before condemning the sensor.
- If the circuits are sound and the fault returns, follow the manufacturer's test procedure to confirm whether the Bank 1 Sensor 3 sensing element has failed.
Common fixes
- Repair damaged or poorly seated Bank 1 Sensor 3 wiring or connector pins.
- Repair an exhaust leak or other source of contamination affecting the sensor, if found.
- Replace the Bank 1 Sensor 3 NOx sensor if circuit checks pass and its sensing element is confirmed faulty.
- Clear the code and verify NOx readings and readiness after repair.
Can I keep driving?
You can usually drive cautiously if the engine runs normally, but avoid prolonged driving because inaccurate NOx readings can increase emissions and may trigger an aftertreatment warning. Arrange diagnosis soon, especially if an emissions test is due.
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.