P201A — Reductant Injection Valve Circuit Range/Performance (Bank 2 Unit 1)
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.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Reductant injection valve
- Reductant metering unit
- Scr catalyst
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- DEF crystallisation clogs the dosing nozzle
- DEF supply pressure below target
- Valve coil ageing — slow response
Possible 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)
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- Reduced-power or limp mode may occur
Related codes
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.