A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.
Possible causes
- The heater’s fuel dosing pump or its line
- The heater’s glow plug (glow pin)
- Carbon in the combustion chamber, or a blocked heater air intake or exhaust
- Summer diesel in freezing weather
What you can do yourself
- This is a built-in diesel-fuelled heater (Webasto, Eberspächer and similar): it doesn’t affect how the engine runs.
- Keep the tank more than a quarter full and check the heater fuse.
- If the heater smokes or smells of fuel, switch it off and don’t use it until it’s repaired.
The explanation comes from the error code reference in the AvtoElektrik PRO app.