Powertrain
generic / SAE
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.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / BA
Possible causes
- Heater element failed high
- Tank temperature sensor drift medium
- Heater relay failed low
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)
Inspection / repair
- Difficulty: hard
- DIY: shop recommended
- Estimated cost: 200–1500 €
- Estimated time: 1–5 h
- Component: reductant tank heater
- Component: reductant line heater
- Component: reductant temperature sensor
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012