OBD-II code · Powertrain (generic, extended)
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.
Is it safe to drive with P20BA?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyHeater element failed
- PossibleTank temperature sensor drift
- Less likelyHeater relay failed
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)
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Reductant Tank Heater, Reductant Line Heater, Reductant Temperature Sensor
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.