Code result
P20B9
Reductant Heater A Control Circuit/Open
Moderate severity
What it means
Reductant heater A (typically the supply line heater nearest the tank) control circuit is open — that segment of DEF line will not be kept above freezing in winter.
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 winding open
highOne of the most commonly reported causes for this code — check this first.
Pin pushed back out of connector body
lowLess common, but worth ruling out after the more likely causes.
Cracked solder joint inside the module or sensor
lowLess common, but worth ruling out after the more likely causes.
Related help
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