P20BA — Reductant Heater A Control Performance
The reductant (AdBlue/DEF) tank or line heater A does not reach the expected temperature within the calibrated time window. In cold weather frozen DEF blocks the SCR dosing system and the engine enters a no-restart state after ignored warnings.
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 tank heater
- Reductant line heater
- Reductant temperature sensor
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Heater element failed
- Tank temperature sensor drift
- Heater relay failed
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
- A drive cycle may be required after repair
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.