OBD-II code · Powertrain (generic, extended)
P221C Reductant Heater B Current Too Low
Reductant Heater B Current Too Low: the control module has detected this fault condition. The reductant (DEF/AdBlue) heater keeps the urea fluid from freezing; a fault can impair SCR dosing in cold conditions.
Is it safe to drive with P221C?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyElement partially open
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
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.7–3 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Line Heater B
Related codes
- P215EReductant Heater D Current Too Low
- P21DDReductant Heater A Current Too Low
- P221EReductant Heater C Current Too Low
- P2219NOx Sensor Heater Control Circuit Low (Bank 2)
- P221ANOx Sensor 1/2 Correlation (Bank 1)
- P221BNOx Sensor 1/2 Correlation (Bank 2)
- P221DReductant Heater B Current Too High
- P221FReductant Heater C Current Too High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.