Code result
P21CD
Reductant Quality Module Supply Voltage Low
Moderate severity
What it means
Supply voltage at the dedicated DEF quality sensor module is below the lower threshold.
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
Voltage drop in supply harness
highOne of the most commonly reported causes for this code — check this first.
Related help
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