Verified boiler fault code
Viessmann A4 Fault Code (Vitodens 222F fault-code checker row)
Air lock in the internal circulation pump or minimum flow rate not achieved.
Safety disclaimer
Fault code summary
- Manufacturer
- Viessmann
- Fault code
- A4
- Fault type
- Pump, Circulation
- Severity
- high
- Reset
- Not specified
- Applicable models
- Vitodens 222F
Quick answer
Air lock in the internal circulation pump or minimum flow rate not achieved.
What does this fault code mean?
Air lock in the internal circulation pump or minimum flow rate not achieved.
Common causes
- Air lock in the internal circulation pump.
- Minimum flow rate not achieved.
Symptoms
- Burner blocked; the venting program starts automatically.
What can the homeowner safely check?
This information was not provided in the verified manufacturer source.
Boiler reset information
Reset information was not provided in the verified manufacturer source. Do not repeatedly reset an unresolved fault.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- Assess pump circulation and minimum flow.
Applicable boiler models
Related fault codes
No related verified fault codes are available for this range.
Manufacturer documentation
Viessmann UK Fault CodesFault Code A4 | Vitodens 222F | Burner blocked. The venting program is started automatically | Air lock in the Internal circulation pump or minimum flow rate not achieved
Last verified
2026-09-12
Frequently asked questions
What does Viessmann A4 mean?
Air lock in the internal circulation pump or minimum flow rate not achieved.