OBD-II code · Powertrain (generic, extended)
P20AC Reductant Metering Unit Temperature Sensor Circuit
A general electrical fault is reported on the temperature sensor inside the DEF metering unit — used to protect the unit from over-temperature and to compensate for fluid viscosity.
Is it safe to drive with P20AC?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelySensor element failed
- PossibleHarness 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, Reductant Metering Temp Sensor
Related codes
- P20A9Reductant Injection Air Pressure Control Valve Circuit High
- P20AAReductant Injection Air Pressure Control Valve Stuck Open
- P20ABReductant Injection Air Pressure Control Valve Stuck Closed
- P20ADReductant Metering Unit Temperature Sensor Circuit Range/Performance
- P20AEReductant Metering Unit Temperature Sensor Circuit Low
- P20AFReductant Metering Unit Temperature Sensor Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.