Viessmann Boiler Fault Codes — BC Reference Guide
F-prefix faults and B-prefix warnings for Viessmann Vitodens 100-W, 200-W, and 222-F series. What each code means, what causes it, and how to respond.
Viessmann's Two-Code System: F-Faults vs B-Warnings
Viessmann uses two distinct code prefixes that behave differently and require different responses:
- F-prefix codes are hard faults. The boiler will lock out and stop operating when an F-code is active. Most F-codes require a technician — attempting multiple resets without identifying the root cause can mask the problem and potentially cause secondary damage.
- B-prefix codes are advisory warnings. The boiler continues to operate normally when a B-code is displayed. These are maintenance reminders or minor operational notifications that should be addressed at your next scheduled service visit (or sooner for B9 condensate faults in cold weather).
Viessmann's Vitotronic 200 and 300 control systems (found in Vitodens 200-W and 222-F) support sub-codes that provide more specific fault information beyond the main F/B code. Reading sub-codes requires a Viessmann service tool and is part of our standard diagnostic procedure.
If you detect a gas smell, do not attempt any resets. Evacuate, call FortisBC at 1-800-663-9911, and wait for clearance before re-entering.
F-Prefix Fault Codes (Lockout Faults)
| Code | Name | Meaning | Common Cause | DIY Check? | Urgency |
|---|---|---|---|---|---|
| F0 | Internal Fault | The Vitotronic control board has detected an internal electronics fault. | PCB component failure, sensor input causing false reading, or power supply issue. | No — requires Viessmann diagnostic interface to read sub-codes. | High |
| F4 | No Ignition | The burner failed to ignite after the permitted number of attempts. | Failed igniter, gas valve fault, low gas pressure, or blocked flue/intake. | Partial — single reset permitted. Check gas supply to other appliances first. | High |
| F10 | Sensor Short Circuit | A temperature sensor circuit is shorted (reading abnormally low resistance). | Damaged sensor, wiring fault, or moisture ingress in the sensor connection. | No — sensor and wiring inspection required. | Moderate |
| F11 | Sensor Open Circuit | A temperature sensor circuit has broken (reading infinite resistance). | Sensor failure, broken wiring, or corroded connector. | No — wiring and sensor continuity test required. | Moderate |
| F73 | Water Pressure Too Low | System water pressure has fallen below the minimum operating threshold (typically 0.8 bar). | Expansion tank bladder failure, slow system leak, or auto-fill valve fault. | Partial — check pressure gauge. If above 0.5 bar, try repressurising via fill valve. If pressure drops again, call a technician. | Moderate |
| F75 | Pump Fault | The internal circulator pump is not running or not moving water as expected. | Pump impeller seized, electrical fault to pump motor, or air-locked pump. | No — pump inspection and electrical test required. | High |
| F83 | Frost Protection Active | The unit has activated frost protection mode due to very low water temperature. | Extended power outage in cold weather, heating system turned off during a cold snap. | Partial — ensure the boiler has power and heating is enabled. Monitor pressure after restart. | Moderate |
B-Prefix Warning Codes (Boiler Continues to Operate)
| Code | Name | Meaning | Common Cause | DIY Check? | Urgency |
|---|---|---|---|---|---|
| B0 | Maintenance Due | The annual service interval has been reached. The boiler continues to operate. | Maintenance timer reached programmed interval. | Yes — this is a maintenance reminder, not a fault. Schedule annual service. | Low — schedule service soon |
| B4 | Chimney Sweep / Flue Gas Test Mode | The boiler is operating in full-load mode for flue gas measurement. | Mode activated by a technician during commissioning or annual inspection. | Partial — if this appears unexpectedly after a service visit, it was likely not cleared. Can be reset via controls. | Low |
| B9 | Condensate Fault | The condensate drain path is restricted or blocked. | Frozen condensate pipe (common in BC winters), blocked condensate trap, or kinked drain hose. | Partial — inspect accessible condensate drain for freezing or blockage. Thaw carefully with warm (not boiling) water. | Moderate — boiler may lock out if condensate backs up. |
Factory-Trained Viessmann Repair in Metro Vancouver
Our technicians carry Viessmann-compatible diagnostic tools and OEM parts. F0, F4, and F73 faults are resolved same-day in most Greater Vancouver service calls.
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