2. Error Codes

Error Codes

If a Baxi boiler develops a problem, the boiler will display an error code to help you identify the issue. The most common of these error codes are explained below.

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Common Error Codes for Baxi Combi and system Boilers

  • 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 
Error codePossible fault
A.00.28Solar temperature sensor is either removed or measures a temperature below range.
A.00.29Solar temperature sensor is either shorted or measures a temperature above range.
A.00.34Outdoor temperature sensor expected but not detected.
A.02.06Low system pressure in heating circuit.
A.02.18OBD error.
A.02.36Functional device disconnected.
A.02.37Passive functional device disconnected.
A.02.45Connection error.
A.02.46Device priority error.
A.02.48Unit function configuration error.
A.02.49Failed node initialisation.
A.02.54OpenTherm bus power supply error.
A.02.55Incorrect or missing serial number.
A.02.76Internal memory reserved for full customisation of settings. No further changes can be made.
E.00.04Return temperature sensor disconnected.
E.00.05Return temperature sensor short circuited.
E.00.16DHW tank temperature sensor not connected.
E.00.17DHW tank temperature sensor short-circuited.
E.00.20The flue gas temperature sensor is not connected or measured a temperature below the range.
E.00.21The flue gas temperature sensor has short-circuited or measured a temperature above the range.
E.01.04Flame loss detected five times in 24 hours.
E.01.12Temperature measured by return sensor greater than flow temperature.
E.01.17No water circulation (permanent).
E.01.20Maximum flue gas temperature reached.
E.02.13Total stoppage of the boiler (antifreeze function not active).
E.02.17Permanent communication failure between gas valve and boiler PCB.
E.02.35Critical safety device disconnected.
E.02.39Minimum pressure not reached after 6 minutes of automatic filling.
E.02.47Connection to external device unsuccessful.
E.04.01Flow temperature sensor short circuited.
E.04.02Flow temperature sensor disconnected.
E.04.03Maximum flow temperature exceeded or flow temperature sensor short circuited.
E.04.08Maximum safe temperature value reached.
E.04.10Burner failed to ignite after 4 attempts.
E.04.12Ignition failure -flame monitoring.
E.04.13Fan impeller blocked or maximum rpm exceeded.
E.04.17Fault in gas valve control circuit.
E.04.18The flow temperature is below the minimum temperature or the flow temperature sensor is not connected.
E.04.23Communication internal stoppage.
E.04.254Fault in gas valve control circuit.
E.04.29Communication internal stoppage.
E.04.54Fault in gas valve control circuit.
H.00.42Pressure sensor open/faulty.
H.00.81Room unit disconnected.
H.01.00Temporary communication failure between gas valve and boiler PCB.
H.01.05Maximum temperature difference value between flow and return reached.
H.01.08Flow temperature increase in heating mode too quick. Temporary stoppage of 10 minutes.
H.01.14Maximum flow or return temperature value reached.
H.01.18No water circulation (temporary).
H.01.21Flow temperature increase during domestic hot water operation too fast.
H.02.00Reset in progress.
H.02.02Waiting for configuration settings to be entered (CN1,CN2).
H.02.03Configuration settings (CN1,CN2) not entered correctly.
H.02.04PCB settings cannot be read.
H.02.05Setting memory not compatible with the boiler PCB type.
H.02.07Low pressure in heating circuit (permanently).
H.02.09Partial stoppage of the boiler (antifreeze function active).
H.02.10Total stoppage of the boiler (antifreeze function not active).
H.02.70 External unit heat recovery test failed.
H.03.00No identification data for boiler safety device.
H.03.02Temporary flame loss.
H.03.05Power supply voltage too low.
H.03.54Temporary flame loss. Shutdown due to the power supply voltage being too low.
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