Powertrain
generic / SAE
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.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / F6
Possible causes
- Valve seat eroded or contaminated high
- Valve plunger seized open medium
- Carbon or debris buildup preventing free movement low
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)
Inspection / repair
- Difficulty: hard
- DIY: shop recommended
- Estimated cost: 200–1500 €
- Estimated time: 1–4 h
- Component: reductant injection valve
- MIL / check engine light
- emissions-relevant
- limp mode possible
Sources
References
sae:J2012