Biasi M90E 28S Fault codes & diagnostics

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

Combi Natural Gas 28 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 28S 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 detected that the water temperature has reached a dangerously high level, causing the system to shut down for safety.

High Engineer only £120-£350

Parts commonly replaced

  • Overheat Stat
  • Water Pump
  • Main Heat Exchanger
Full explanation for 30c
ER + 14 + Reset

Your boiler has stopped working because it has detected an electrical connection issue or a fault with one of its internal control components.

High Engineer only £120-280

Parts commonly replaced

  • Main PCB
  • Wiring Harness
  • Voltage Transformer
Full explanation for ER + 14 + Reset
ER + 25 + Reset

Your boiler has likely detected a circulation issue or caught air in the system, causing it to shut down to prevent overheating.

High DIY-safe £120-280

What to check first

  1. Ensure all radiator valves are fully open
  2. Bleed your radiators to remove any trapped air
  3. Check that your system pressure is topped up to between 1 and 1.5 bar
  4. Press and hold the Reset button for 2 seconds

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger
  • Overheat Thermostat
Full explanation for ER + 25 + Reset
ER + 69

Your boiler has detected an internal electrical communication error, which means the main control board cannot properly speak to other components.

High Engineer only £180-350

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring Harness
Full explanation for ER + 69
ER 01 + Reset

Your boiler has failed to light the gas flame or has lost its flame signal, causing it to lock out for safety.

High DIY-safe £100-280

What to check first

  1. Check that your gas supply is turned on and other gas appliances are working
  2. Press and hold the Reset button for five seconds
  3. Ensure the condensate pipe (if external) isn't frozen in cold weather

Parts commonly replaced

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

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

High DIY-safe £100-250

What to check first

  1. Locate the reset button on the control panel
  2. Turn the selector dial to the 'R' position for a few seconds and then back to 'On'
  3. Check that your radiator valves are open and your boiler 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 £120-£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 is preventing it from heating until more water is added.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually two silver braided hoses) beneath the boiler.
  2. Open the valves slowly until you hear water flowing and watch the pressure gauge.
  3. Close both valves tightly once the needle reaches between 1 and 1.5 bar.

Parts commonly replaced

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

Your boiler has failed to ignite after several attempts and has locked itself out for safety.

High DIY-safe £100-£250

What to check first

  1. Check that your gas supply is turned on and other gas appliances are working
  2. Turn the selector switch to the 'R' position for a few seconds to reset the boiler
  3. Wait for the boiler to restart and check if the flame stays lit

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)
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.

High DIY-safe £0-160

What to check first

  1. Locate the filling loop (a flexible silver hose) underneath the boiler.
  2. Slowly open the tap or taps on the filling loop until you hear water entering the system.
  3. Watch the pressure gauge and close the taps when the needle reaches between 1.0 and 1.5 bar.
  4. Ensure the taps are fully closed and reset the boiler if necessary.

Parts commonly replaced

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