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Common Vaillant fault codes with what each means, the likely cause, and what CANRO Heating & Cooling does to fix them. Servicing Vaillant systems across Metro Vancouver since 1999.
Vaillant ecoTEC plus, ecoFIT Pure, and ecoCOMPACT condensing boilers use F-prefixed fault codes (F.0 to F.99) shown on the digital display. The most common Metro Vancouver Vaillant codes:
Important: One reset attempt is generally safe for transient faults. If the same code returns within minutes, stop resetting — the lockout exists to protect the heat exchanger, ignition system, and gas-valve safety circuit. Note the exact code and call CANRO at (604) 359-1081. We carry common Vaillant parts in every truck — most code-triggered faults are resolved in a single visit.
What it means: Outlet sensor fault.
Common causes: Failed sensor.
What to do: Swap.
Reset guidance: one reset OK
What it means: Return sensor fault.
Common causes: Failed sensor.
What to do: Swap.
Reset guidance: one reset OK
What it means: Outdoor sensor wiring shorted.
Common causes: Wiring or sensor.
What to do: Service.
Reset guidance: one reset OK
What it means: Outdoor sensor open circuit.
Common causes: Wiring or sensor.
What to do: Service.
Reset guidance: one reset OK
What it means: DHW outlet sensor fault.
Common causes: Failed sensor.
What to do: Swap.
Reset guidance: one reset OK
What it means: High-limit tripped.
Common causes: Low flow, scaling.
What to do: Service.
Reset guidance: no
What it means: System pressure too low.
Common causes: Leak, failed sensor.
What to do: Top up; locate.
Reset guidance: top up
What it means: Flow/return temp differential too large.
Common causes: Low flow, failed circulator.
What to do: Service.
Reset guidance: no
What it means: Circulator pump signal abnormal.
Common causes: Failed pump or wiring.
What to do: Pump service.
Reset guidance: no
What it means: Pre-ignition flame detected.
Common causes: Gas valve fault.
What to do: Call immediately.
Reset guidance: no
What it means: Burner did not light.
Common causes: Flame rod, ignitor, gas.
What to do: Standard service.
Reset guidance: one reset OK
What it means: Flame extinguished.
Common causes: Dirty rod, condensate.
What to do: Clean.
Reset guidance: one reset OK
What it means: Combustion fan speed signal abnormal.
Common causes: Failed fan.
What to do: Service.
Reset guidance: no
What it means: Internal bus voltage low.
Common causes: Wiring, control board.
What to do: Service.
Reset guidance: no
What it means: Gas valve drive fault.
Common causes: Failed valve.
What to do: Service.
Reset guidance: no
What it means: Gas valve shutdown timing abnormal.
Common causes: Valve or board.
What to do: Service.
Reset guidance: no
What it means: Control memory.
Common causes: Board.
What to do: Replacement.
Reset guidance: no
What it means: Sensor short circuit.
Common causes: Sensor.
What to do: Swap.
Reset guidance: one reset OK
What it means: Control board over-temp.
Common causes: Excessive ambient or board fault.
What to do: Ventilation, service.
Reset guidance: no
What it means: Flame signal implausible.
Common causes: Flame rod, wiring.
What to do: Service.
Reset guidance: one reset OK
What it means: Display/PCB mismatch after repair.
Common causes: Service comm.
What to do: Service.
Reset guidance: no
What it means: Flow sensor reading invariant.
Common causes: Failed sensor.
What to do: Swap.
Reset guidance: one reset OK
What it means: Sensor differential fault.
Common causes: Failed sensor.
What to do: Swap.
Reset guidance: one reset OK
What it means: Pressure sensor abnormal.
Common causes: Failed sensor.
What to do: Swap.
Reset guidance: one reset OK
What it means: Pressure sensor open.
Common causes: Failed sensor or wiring.
What to do: Swap.
Reset guidance: one reset OK
What it means: Pressure jump on pump start abnormal.
Common causes: Closed valve, air-locked system.
What to do: Service.
Reset guidance: no
What it means: Temperature sensor reading not changing.
Common causes: Failed sensor.
What to do: Swap.
Reset guidance: one reset OK
What it means: Gas type coding error.
Common causes: Configuration issue.
What to do: Service.
Reset guidance: no
Note the exact code on your display, then call CANRO. Most Vaillant faults are diagnosed and repaired on the first visit because we stock common Vaillant service parts in every truck.
📞 Call (604) 359-1081 nowCANRO services Vaillant German condensing boilers and heat pumps in every Metro Vancouver city — including same-day emergency response for no-heat, no-hot-water, and gas-leak situations. See our city-specific Vaillant pages:
→ See the full Vaillant lineup hub page with every model, specs, and install costs
This Vaillant error code guide is maintained by the CANRO Heating & Cooling team based on 25+ years of Vaillant install, service, and repair experience across Metro Vancouver. Codes and behaviour described match current model manuals. Last reviewed May 2026.
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