HVACopedia

Viessmann · Boiler

F.387 Ionization current ground fault

High severity Vitodens 200-W B2HE

What the control is telling you

Burner in a fault state.

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

Likely causes

  • Condensate back-up
  • Wet insulation
  • Electrode/cable fault
  • Faulty BCU

Test and repair steps

  1. Check electrode and cable.
  2. Check for condensate back-up; check the drain and siphon.
  3. Replace insulation blocks, electrodes and flame body if needed; detach fan unit before removing the burner and protect electronics.
  4. If there is no back-up and the fault persists, replace the BCU.
  5. 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.383 Possible gas line contamination
  • F.384 Possible gas line contamination
  • F.385 Short circuit on ionization signal 1
  • F.386 BCU faulty
  • F.388 BCU faulty
  • F.395 IO electrode ground fault
  • F.396 BCU faulty
  • F.399 IO electrode ground fault

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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.