Code result
P21AE
Reductant Level Sensor C Circuit Range/Performance
Moderate severity
What it means
DEF level sensor C reading is in electrical range but plausibility check fails — value sticks, jumps, or does not match consumption.
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 sticks
highOne of the most commonly reported causes for this code — check this first.
Sensor element aged beyond calibration window
lowLess common, but worth ruling out after the more likely causes.
Sensor mounting loose - signal damping
lowLess common, but worth ruling out after the more likely causes.
Related help
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