Code result
P21C6
Reductant Level Sensor B Stuck
Moderate severity
What it means
DEF level sensor B 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.
Is it safe to drive?
Use caution
The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.
Most likely causes
Float arm jammed
highOne of the most commonly reported causes for this code — check this first.
Related help
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