OBD-II code · Powertrain (generic, extended)
P205F Reductant System Performance (Bank 2)
The DEF system as a whole on bank 2 is not delivering the required NOx reduction — NOx-out remains too high relative to commanded dosing across a drive cycle. Causes range from poor DEF quality, restricted dosing line, weak pump, to a degraded SCR catalyst.
Is it safe to drive with P205F?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyPoor DEF quality — diluted or contaminated
- PossibleSCR catalyst thermally aged
- PossibleCrystallisation restricts dosing line
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
- 1.5–8 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Scr Catalyst, Reductant Metering Unit, Reductant Quality Sensor, Reductant Pump
Related codes
- P205CReductant Tank Temperature Sensor A Circuit Low
- P205DReductant Tank Temperature Sensor A Circuit High
- P205EReductant Tank Temperature Sensor A Circuit Intermittent/Erratic
- P2060Reductant Injection Air Pump Control Circuit Low
- P2061Reductant Injection Air Pump Control Circuit High
- P2062Reductant/Regeneration Supply Control Circuit/Open
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.