Code result
P05F8
Reductant Heater Control Module Performance
Moderate severity
What it means
The reductant heater module is electrically intact but does not deliver the expected thermal effect - heater elements aged, supply line resistance, or thermostat sensor offset.
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 element aged
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Module software outdated, reflash may resolve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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