Sprinter Repair Guides
Why Sprinter DEF Heaters Fail And Trigger Cold-Weather Faults
Updated 2026-01-26
The DEF tank heater keeps AdBlue from freezing so it can be dosed. When it fails, the Sprinter throws a DEF fault and can begin counting down your starts, often in cold weather. Replacing the heater and resetting the system clears the fault at its source.
The heater's job
AdBlue freezes in the cold, so the tank heater thaws it for dosing. A failed heater looks to the van like a system fault.
Fixing it right
We confirm the heater circuit before replacing it, then reset the count only after the repair, so the warning does not immediately return.