Baxi · Combi & System 2 platform
H.01.00Temporary communication failure between gas valve and boiler PCB
This code applies to Baxi 200 Combi 2, Baxi 400 Combi 2, Baxi 600 Combi 2, Baxi 800 Combi 2, Baxi Assure 500 Combi 2, Baxi 600 System 2, Baxi 800 System 2, Baxi Assure 500 System 2. Fault codes narrow down the likely problem, but they do not replace a model-specific diagnosis.
What you can safely check
- Do not keep resetting the boiler or open its case.
- Arrange a Gas Safe registered engineer.
- If you smell gas, leave the property and call the National Gas Emergency Service on 0800 111 999 from outside.
How an engineer may fix it
Isolate and test the gas valve circuit, valve tightness, ignition or flame-sensing system and control board; repair or replace components and complete required gas-safety checks.
Manufacturer source: Baxi Professional — Boiler Error Codes. Checked 15 August 2026. The appliance manual and an engineer’s on-site diagnosis take precedence. Never remove the boiler case yourself.