What it means
NOx Sensor Heater Control Circuit Low (Bank 2): the control-circuit voltage is below 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 has an electric heater that brings the sensor up to operating temperature so it can report nitrogen oxide levels to the emissions control module. This code sets when the heater control circuit voltage is lower than expected, which can delay reliable NOx readings and affect SCR control.
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
- Read freeze-frame data and check whether the fault returns during a cold start, when the bank 2 NOx sensor heater is expected to operate.
- Inspect the bank 2 NOx sensor connector and nearby harness for corrosion, loose pins, or insulation worn through against the chassis or exhaust.
- With the circuit safely isolated as specified by the manufacturer, check the heater control wire for an unintended path to ground.
- Check the connector terminals and heater circuit for excessive resistance or poor contact, comparing measurements with the manufacturer's specification.
- If the wiring and connections pass, test the bank 2 NOx sensor heater and its control circuit according to the manufacturer's procedure.
Common fixes
- Repair chafed bank 2 NOx sensor heater wiring that is shorted to ground.
- Clean or repair corroded or loose terminals at the bank 2 NOx sensor connector.
- Repair damaged heater circuit wiring and restore secure connections.
- 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 ignoring the NOx warning or taking unnecessary long trips. Inaccurate emissions readings can affect SCR operation, 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.