OBD-II code · Powertrain (generic, extended)
P20B6 Reductant Metering Unit Heater Control Circuit Performance
Metering unit heater is electrically OK but does not warm the block within the expected time — partial winding fault or excessive heat loss.
Is it safe to drive with P20B6?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyPartial winding fault
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
- 1–4 h
- Emissions test
- Likely to fail
- Parts involved
- Reductant Metering Unit Heater
Related codes
- P20B5Reductant Metering Unit Heater Control Circuit/Open
- P20B3Reductant Heater Coolant Control Valve Circuit Low
- P20B4Reductant Heater Coolant Control Valve Circuit High
- P20B7Reductant Metering Unit Heater Control Circuit Low
- P20B8Reductant Metering Unit Heater Control Circuit High
- P20B9Reductant Heater A Control Circuit/Open
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.