What it means
Reductant Injection Valve Circuit Range/Performance (Bank 2 Unit 1): the signal is implausible or outside the valid range. This valve doses reductant (DEF/AdBlue) into the exhaust for SCR NOx reduction.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The reductant injection valve for bank 2, unit 1 meters DEF/AdBlue into the exhaust so the SCR system can reduce nitrogen oxides. The control module evaluates the valve circuit and dosing response; P201A sets when that response is outside the expected range, which can result from a restricted nozzle, low supply pressure, or slow valve operation.
Common causes
Most likely first.
- DEF crystallisation clogs the dosing nozzle
- DEF supply pressure below target
- Valve coil ageing — slow response
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 SCR/NOx live data, and note any DEF quality, pressure, or inducement countdown warnings associated with the fault.
- Inspect the bank 2 unit 1 dosing valve, its connector, and nearby exhaust area for DEF crystals, leaks, corrosion, or damaged wiring.
- Check DEF supply pressure and commanded versus actual dosing using the vehicle's available scan-tool data and manufacturer's test procedure.
- If supply pressure is low, inspect the related pump, lines, and filter for restrictions or leaks before condemning the dosing valve.
- Test the valve circuit and response to the manufacturer's specification; clean or replace the valve only after confirming the fault is at the injector.
Common fixes
- Clean DEF crystals from the bank 2 unit 1 dosing nozzle using the manufacturer's service method.
- Repair a leaking or restricted DEF supply line or connection causing pressure below target.
- Repair corroded or damaged valve wiring and connector terminals.
- Replace the bank 2 unit 1 reductant injection valve if its coil or dosing response fails testing.
Can I keep driving?
The vehicle may enter reduced-power operation or start a no-start countdown if the SCR fault remains, so avoid long trips and do not ignore DEF or NOx warnings. Arrange diagnosis promptly; continued driving can leave the vehicle unable to restart and cause an emissions inspection failure.
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.