Code result
P21CE
Reductant Quality Module Performance
Moderate severity
What it means
DEF quality module reports an internal performance fault — self-test failed or measurement loop unable to converge. The module may need replacement.
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
Internal module fault
highOne of the most commonly reported causes for this code — check this first.
Module software outdated, reflash may resolve
lowLess common, but worth ruling out after the more likely causes.
Supply voltage outside specification
lowLess common, but worth ruling out after the more likely causes.
Related help
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