U01B6Lost Communication With Fuel Heater Control Module
- Generic OBD-II code · Network
- How the car detects it
- A fuel heater warms diesel ahead of the filter so that paraffin wax, which separates out in the cold, cannot clog the element; ordinary diesel turns to gel at roughly −15 to −19 °C. Newer designs use a microcontroller: a patent describes a heater controller that sets power from outside air temperature in open loop or from fuel temperature in closed loop, and cuts out when battery voltage falls too low. Where such a unit reports to the engine controller over the network, U01B6 means it has stopped answering and the heater state is unknown. No manufacturer documents this code publicly, and whether a MIL follows depends on how the maker rates the heater for emissions. In frost, expect hard starting, power loss or stalling from a waxed filter; in mild weather often nothing is noticed.
- What you may notice
- Hard starting or stalling in frost
- Power loss from a clogged fuel filter in cold weather
- Often no symptom in mild weather
- Likely causes
- LikelyCorroded or loose connector at the filter housing heater
- PossibleHeater module supply fuse or relay failed
- RareFuel heater control electronics faulty
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.