HVACopedia

Viessmann · Boiler

F.385 Short circuit on ionization signal 1

High severity Vitodens 200-W B2HE

What the control is telling you

Burner in a fault state; BCU possibly faulty.

Applies to: Vitodens 200-W B2HE 85, 120, 150, 199

Likely causes

  • Electrode/cable short
  • Faulty BCU

Test and repair steps

  1. Check ionization electrode and cable.
  2. If it persists, replace the BCU.
  3. Reset the appliance.

Models that show this code

4 models in Vitodens 200-W B2HE

B2HE-120B2HE-150B2HE-199B2HE-85

Other codes on the same units

  • F.381 Flame loss during operation
  • F.382 Error counter limit exceeded
  • F.383 Possible gas line contamination
  • F.384 Possible gas line contamination
  • F.386 BCU faulty
  • F.387 Ionization current ground fault
  • F.388 BCU faulty
  • F.395 IO electrode ground fault

Save it for the next call

Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.

Open the app

Source: Viessmann Vitodens 200-W B2HE 85/120/150/199 Service Instructions 6167 813-24 (09/2026), Fault messages, p.62-73. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.