What it means
The DEF injection valve at bank 2 unit 1 does not open when commanded — typically crystallised DEF blocks the nozzle, no flow into the SCR.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The reductant injection valve at bank 2 unit 1 meters DEF into the exhaust to help the SCR system reduce NOx. The module monitors the valve response and sets this code when the bank 2 unit 1 valve does not open as commanded, preventing expected DEF flow.
Common causes
Most likely first.
- Nozzle crystallised
- Carbon or debris buildup preventing free movement
- Component wear with age - mechanical play
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 SCR or DEF warnings to identify when the bank 2 unit 1 valve failed to respond.
- Inspect the bank 2 unit 1 injector nozzle and nearby exhaust for crystallised DEF or deposits.
- Check the valve connector and wiring for damage, corrosion, or a loose connection.
- Use the manufacturer's procedure to command the valve and confirm whether it actuates and delivers DEF.
- If the electrical circuit operates but flow is absent, inspect the valve for seizure, blockage, or mechanical wear using the manufacturer's service procedure.
Common fixes
- Clean crystallised DEF from the bank 2 unit 1 nozzle using the manufacturer's service guidance.
- Repair a poor electrical connection or damaged wiring to the valve.
- Replace the bank 2 unit 1 reductant injection valve if it is seized, worn, or remains blocked.
- Verify SCR dosing and clear related faults after repair.
Can I keep driving?
If the vehicle is in reduced-power mode, avoid driving except as needed to reach a safe place. A closed bank 2 unit 1 injector impairs NOx control, and continued driving may bring emissions restrictions or a no-start countdown.
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.