Powertrain
generic / SAE
P21C5
Reductant Level Sensor A Stuck
DEF level sensor A reading does not change over a refill or consumption window — float arm jammed or sender wiper stuck. Distinct from a circuit fault because the electrical signal stays plausible.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number1 / C5
Possible causes
- Float arm jammed by debris or crystallisation high
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: 120–800 €
- Estimated time: 1–4 h
- Component: reductant level sensor
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012