What it means
The supply voltage rail to the NOx sensor on bank 1 sensor 1 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 1 NOx sensor needs a stable electrical supply for its heater and measuring electronics. P220A sets when the control module detects a problem with that sensor's supply voltage circuit, which may come from wiring, a connector, a fuse, or the sensor itself.
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
- Check freeze-frame data and related supply or sensor codes to identify when the bank 1 sensor 1 supply fault occurs.
- Locate the bank 1 sensor 1 and inspect its connector and supply wiring for corrosion, looseness, exhaust heat damage, or chafing.
- Use the wiring diagram to identify and check the relevant fuse and supply connections, without replacing a fuse until the circuit is inspected for a short.
- Measure supply and ground at the sensor connector under the conditions specified by the manufacturer, and compare results with its specification.
- If the supply wiring and fuse are sound, test for an internal sensor fault and verify the control module feed using the manufacturer's circuit procedure.
Common fixes
- Clean and secure the bank 1 sensor 1 supply connector.
- Repair damaged, open, or shorted supply wiring.
- Replace a blown fuse after correcting the cause of the overcurrent.
- Restore a faulty supply or ground connection.
- Replace the bank 1 sensor 1 NOx sensor if it is internally shorted or fails specified tests.
Can I keep driving?
The engine may remain drivable, but the bank 1 sensor 1 may not heat or measure NOx reliably, increasing emissions and risking an inspection failure. If an AdBlue/DEF warning or start countdown appears, get the circuit checked 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.