What it means
NOx Sensor Heater Control Circuit High (Bank 2): the control-circuit voltage is above the expected range. The NOx sensor heater brings the sensor to operating temperature; a fault delays accurate NOx readings used for SCR control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The NOx sensor on bank 2 uses an electric heater to reach operating temperature so the emissions control module can rely on its readings for SCR control. This code sets when the heater control circuit voltage is higher than expected, which can prevent correct heater operation and delay accurate NOx readings.
Common causes
Most likely first.
- Short to B+
- 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
- Review freeze-frame data and live readings to confirm whether the bank 2 NOx sensor heater circuit reports high voltage during a heater command.
- Inspect the bank 2 sensor harness for pinching or chafing where a supply wire could contact a power source.
- Check the bank 2 NOx sensor connector for corrosion, loose terminals, or contamination that could affect the circuit.
- With the circuit isolated as specified by the manufacturer, test the heater control wiring for a short to battery voltage.
- If the wiring and connector pass, test the bank 2 NOx sensor heater and control circuit according to the manufacturer's procedure.
Common fixes
- Repair the bank 2 NOx sensor heater wire shorted to a power source.
- Repair a pinched or chafed harness near the bank 2 sensor.
- Clean or repair corroded or loose terminals at the bank 2 sensor connector.
- Replace the bank 2 NOx sensor if its heater fails the specified test.
Can I keep driving?
If the vehicle runs normally, a short trip to arrange diagnosis may be possible, but avoid unnecessary long trips while the NOx warning is active. Incorrect readings can disrupt SCR control, trigger a DEF warning, or lead to a no-start countdown on vehicles that use one.
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.