Powertrain
generic / SAE
P20B9
Reductant Heater A Control Circuit/Open
Reductant heater A (typically the supply line heater nearest the tank) control circuit is open — that segment of DEF line will not be kept above freezing in winter.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / B9
Possible causes
- Heater winding open high
- Pin pushed back out of connector body low
- Cracked solder joint inside the module or sensor 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: medium
- DIY: shop recommended
- Estimated cost: 80–800 €
- Estimated time: 0.7–3 h
- Component: reductant line heater a
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012