What it means
The bank 1 sensor 2 NOx sensor heater sense circuit signal is below the expected range. The code alone does not identify the cause.
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 after the engine’s first cylinder bank; its heater brings the sensing element to operating temperature. The control module monitors the heater sense circuit, and this code sets when its signal is lower than expected, which may result from a short to ground, damaged insulation, or a poor connector contact.
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
- Record freeze-frame data and check related NOx and heater codes to establish whether the low reading is limited to Bank 1 Sensor 2.
- With the exhaust cool, inspect the sensor connector and harness for corrosion, loose pins, chafing, or wiring touching ground or metal.
- Check the connector terminals for damage or corrosion that could raise resistance in the heater sense circuit.
- Following the wiring diagram, test the heater sense wire for a short to ground and check continuity through the circuit as specified by the manufacturer.
- If the wiring passes, test the heater and sense element using the manufacturer's procedure before condemning the sensor.
Common fixes
- Repair heater sense wiring that is chafed through or shorted to ground.
- Clean or repair corroded or loose Bank 1 Sensor 2 connector terminals.
- Replace a damaged harness or connector section.
- Replace the Bank 1 Sensor 2 NOx sensor if its heater sense element fails the specified tests.
Can I keep driving?
If the vehicle drives normally, a short trip to arrange diagnosis is generally reasonable, but avoid extended use with the emissions warning active. The NOx or AdBlue/DEF warning may progress to a no-start countdown, and the vehicle may fail an emissions inspection.
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.