Powertrain
generic / SAE
P20B5
Reductant Metering Unit Heater Control Circuit/Open
The control circuit for the heater inside the DEF metering unit is open — winter operation cannot keep the dosing block above freezing.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / B5
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: hard
- DIY: shop recommended
- Estimated cost: 200–1500 €
- Estimated time: 1–4 h
- Component: reductant metering unit heater
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012