Biasi M90E 24S Fault codes & diagnostics

10 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Combi Natural Gas 24 kW 2003-2010 Discontinued

Replaced by: Advance

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
10 High
Just want the most common Biasi M90E 24S faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 10 documented codes

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30c

Your boiler has likely detected an overheating issue which has caused it to shut down to prevent damage.

High DIY-safe £90-250

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure is between 1.0 and 1.5 bar
  3. Press the reset button on the front control panel
  4. Allow the boiler to cool down for 20 minutes before restarting

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Temperature Sensor (NTC)
Full explanation for 30c
ER + 14 + Reset

Your boiler has detected an internal communication error or a control board fault that is preventing it from running safely.

High Engineer only £180-350

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring Harness
Full explanation for ER + 14 + Reset
ER + 25 + Reset

Your boiler has likely detected a circulation or overheating issue, meaning water isn't moving through the system correctly to keep it cool.

High DIY-safe £120-350

What to check first

  1. Check that your system pressure is between 1.0 and 1.5 bar on the pressure gauge
  2. Ensure all radiator valves are fully open, including those on towel rails
  3. Press and hold the Reset button for 2-5 seconds to see if the fault clears

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • NTC Temperature Sensor
Full explanation for ER + 25 + Reset
ER + 69

Your boiler has detected an internal communication failure between the electronic control boards, meaning it cannot process commands to provide heating or hot water.

High Engineer only £180-350

Parts commonly replaced

  • Main PCB
  • Display PCB
  • Wiring Harness
Full explanation for ER + 69
ER 01 + Reset

Your boiler has failed to ignite or has lost its flame, causing the system to lock out for safety.

High DIY-safe £100-350

What to check first

  1. Check if other gas appliances, like a cooker, are working to confirm gas supply
  2. Ensure the condensate pipe (outside) is not frozen if it is winter
  3. Turn the selector switch to the 'Reset' position, wait five seconds, then turn it back to the 'On' position

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • PCB
Full explanation for ER 01 + Reset
ER 02 + Reset

Your boiler has likely overheated, causing the safety system to shut it down to prevent damage.

High DIY-safe £100-280

What to check first

  1. Locate the reset button on the control panel.
  2. Press and hold the reset button for a few seconds until the fault light clears.
  3. Ensure your radiator valves are open and that the system pressure is between 1 and 1.5 bar.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger
Full explanation for ER 02 + Reset
ER 03 + Reset

Your boiler has detected a problem with how it disposes of waste gases, causing it to shut down for safety.

High Engineer only £100-280

Parts commonly replaced

  • Air Pressure Switch
  • Fan Assembly
  • Venturi Tube
Full explanation for ER 03 + Reset
ER 10 + reset

Your boiler has detected low water pressure in the system, which means there isn't enough water to circulate and provide heating or hot water safely.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually two small valves connected by a silver braided hose) underneath the boiler.
  2. Slowly open both valves and watch the pressure gauge needle rise.
  3. Close both valves tightly once the pressure gauge reaches between 1.0 and 1.5 bar.

Parts commonly replaced

  • Filling loop valve
  • Pressure sensor
  • Expansion vessel
Full explanation for ER 10 + reset
Li

Your boiler has detected that the water inside has become far too hot, causing the system to shut down safely to prevent damage.

High DIY-safe £100-280

What to check first

  1. Wait at least 30 minutes for the boiler to cool down naturally.
  2. Locate the manual reset button on the control panel.
  3. Press and hold the reset button for a few seconds to clear the lockout.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Temperature Sensor (NTC)
Full explanation for Li
LP

Your boiler has detected that the water pressure is too low for it to operate safely and has shut down as a result.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually a silver braided hose with small valves) underneath the boiler.
  2. Slowly open the valve(s) until you hear water entering the system.
  3. Watch the pressure gauge and close the valves tightly once the needle reaches between 1 and 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Pressure switch
  • Expansion vessel
Full explanation for LP