OBD-II code · Powertrain (generic, extended)
P204F Reductant System Performance
The SCR (selective catalytic reduction) system using AdBlue/DEF is not delivering the expected NOx conversion. Causes range from poor reductant quality, dosing module faults, heater failure on the AdBlue tank in cold weather, or a degraded SCR catalyst.
Is it safe to drive with P204F?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyPoor reductant quality or contamination
- PossibleDosing module clogged with urea crystals
- PossibleSCR catalyst aged or contaminated
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
- 1–6 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Scr Catalyst, Adblue Dosing Module, Adblue Tank Heater, Nox Sensor
Related codes
- P204CReductant Pressure Sensor Circuit Low
- P204DReductant Pressure Sensor Circuit High
- P204EReductant Pressure Sensor Circuit Intermittent/Erratic
- P2050Reductant Injection Valve Circuit/Open (Bank 2 Unit 1)
- P2051Reductant Injection Valve Circuit Low (Bank 2 Unit 1)
- P2052Reductant Injection Valve Circuit High (Bank 2 Unit 1)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.