Code result
P20ED
Reductant Heater "A" Control Stuck On
Moderate severity
What it means
The reductant tank heater "A" stays energised even when not commanded — usually a shorted driver stage. Continuous heating wastes current and can overheat the heater element.
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
Heater driver shorted on
highOne of the most commonly reported causes for this code — check this first.
Heater line shorted to positive
mediumA plausible cause — test and verify before replacing parts.
Carbon or debris buildup preventing free movement
lowLess common, but worth ruling out after the more likely causes.
Related help
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