What it means
The supply voltage rail to the NOx sensor on bank 1 sensor 2 is faulty — typically a fuse, harness break, or short. NOx sensors need a clean stable supply for the heater and the wide-band measurement cell.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The bank 1 sensor 2 NOx sensor relies on a stable supply for its heater and measuring electronics. P220B indicates a fault in that sensor's supply voltage circuit; it points to the sensor 2 feed specifically, which may be affected by its wiring, connector, fuse, or sensor.
Common causes
Most likely first.
- Open or short in the sensor power wiring
- Poor electrical connection or corroded connector
- Blown fuse or faulty power supply
- NOx sensor internal fault
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 codes to determine when the bank 1 sensor 2 supply fault was detected.
- Identify the bank 1 sensor 2 location from vehicle information and inspect its connector and harness for corrosion, loose terminals, heat damage, or chafing.
- Check the fuse and supply path assigned to the bank 1 sensor 2 circuit using the wiring diagram, and look for a short before fitting a replacement fuse.
- Measure supply and ground at the bank 1 sensor 2 connector under the manufacturer's specified conditions and compare with the manufacturer's specification.
- If the circuit feed is good, test the sensor for an internal supply fault and verify the module feed using the specified circuit procedure.
Common fixes
- Reconnect or clean the bank 1 sensor 2 supply connector.
- Repair open, shorted, or heat-damaged sensor 2 supply wiring.
- Replace a failed fuse after locating and correcting the reason it opened.
- Repair a faulty ground or supply connection in the sensor 2 circuit.
- Replace the bank 1 sensor 2 NOx sensor if it fails internal circuit tests.
Can I keep driving?
The vehicle may still run, but the bank 1 sensor 2 may not heat or report NOx correctly, which can compromise emissions control and inspection results. Take any DEF warning or start countdown seriously and arrange repair promptly.
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.