OBD-II code · Powertrain (generic, extended)
P20F6 Reductant Injection Valve Stuck Open (Bank 1 Unit 1)
The DEF injection valve at bank 1 unit 1 does not close when commanded — DEF flows continuously into the SCR. Risk of crystallisation in the catalyst and over-dosing.
Is it safe to drive with P20F6?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyValve seat eroded or contaminated
- PossibleValve plunger seized open
- Less likelyCarbon or debris buildup preventing free movement
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 Injection Valve
Related codes
- P20F7Reductant Injection Valve Stuck Open (Bank 2 Unit 1)
- P20F3SCR NOx Pre-Catalyst Efficiency Below Threshold (Bank 2)
- P20F4Reductant Consumption Too Low
- P20F5Reductant Consumption Too High
- P20F8Intake Manifold Runner Control Circuit Performance (Bank 1)
- P20F9Intake Manifold Runner Control Circuit Performance (Bank 2)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.