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.
Affected components
- Reductant metering unit heater
Common causes
- High likelihood: Heater winding open
- Low likelihood: Pin pushed back out of connector body
- Low likelihood: Cracked solder joint inside the module or sensor
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
Sources
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.