Biasi Activa Fault codes & diagnostics

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

Combi Natural GasLPG 24-30 kW 2009-2012 Discontinued

Replaced by: Advance

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 23 High 3 Medium 2 Low
Just want the most common Biasi Activa faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 29 documented codes

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90˚C

Your boiler is overheating because the water inside is getting too hot, causing it to automatically turn down its power to prevent damage.

Medium DIY-safe £100-250

What to check first

  1. Check that all radiator valves are fully open to allow water to flow.
  2. Ensure the boiler pressure gauge is between 1 and 1.5 bar.
  3. Reset the boiler using the control knob to see if the fault clears.

Parts commonly replaced

  • Circulation pump
  • Primary thermistor (NTC sensor)
  • Main heat exchanger (de-scaling)
Full explanation for 90˚C
110˚C

Your boiler has sensed that the exhaust gases are getting too hot and has shut itself down as a safety precaution.

High Engineer only £120-350

Parts commonly replaced

  • Flue Thermistor
  • Main Heat Exchanger
  • Gas Valve
Full explanation for 110˚C
E01

Your boiler has failed to light the gas flame, meaning it has shut itself down for safety and cannot provide heating or hot water.

High DIY-safe £100-£350

What to check first

  1. Check if your gas supply is active by testing another gas appliance like a hob.
  2. Perform a reset by turning the control knob to 'R' for five seconds and then back to the on position.
  3. Verify that your condensate pipe (the plastic pipe leading outside) isn't frozen if it is currently winter.

Parts commonly replaced

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

Related codes

Full explanation for E01
E02

Your boiler has switched itself off because it has detected that it is getting too hot inside.

High DIY-safe £100-280

What to check first

  1. Check that all radiator valves are open to ensure water can flow.
  2. Ensure there are no blockages in the system by checking for trapped air in radiators.
  3. Press the Reset button on the boiler control panel once to see if it restarts.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Thermistor (NTC Sensor)

Related codes

Full explanation for E02
E03

Your boiler has detected that there is not enough water or water pressure to operate safely, causing it to shut down.

High DIY-safe £80-£220

What to check first

  1. Locate the pressure gauge on the front of your boiler.
  2. If the needle is below 1, find the filling loop valves underneath the boiler.
  3. Slowly open both valves to top up the system until the gauge reaches between 1 and 1.5 bar, then close them tightly.

Parts commonly replaced

  • Primary flow switch
  • Water pressure sensor
  • Circulating pump

Related codes

Full explanation for E03
E04

Your boiler is unable to move water around the system properly, which has caused it to shut down to prevent overheating.

High DIY-safe £180-£350

What to check first

  1. Check that your central heating valves (under the boiler) are fully open
  2. Ensure all radiator valves are turned on and not closed
  3. Check if the boiler pressure gauge is between 1.0 and 1.5 bar
  4. Gently bleed your radiators to remove any trapped air pockets

Parts commonly replaced

  • Circulation pump
  • Flow switch
  • Primary heat exchanger (de-scaling)

Related codes

Full explanation for E04
E05

Your boiler is unable to safely clear exhaust fumes or draw in fresh air, causing it to shut down for safety.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Venturi tube

Related codes

Full explanation for E05
E06

Your boiler is struggling to accurately measure the temperature of the water inside the system, which is preventing it from heating up correctly.

High Engineer only £90-160

Parts commonly replaced

  • Central heating temperature sensor (NTC thermistor)
  • Connecting wiring harness

Related codes

Full explanation for E06
E07

Your boiler is struggling to accurately measure the temperature of the water coming out of your taps, which usually means your hot water will be inconsistent or not work at all.

Medium Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC thermistor
  • Wiring harness connectors

Related codes

Full explanation for E07
E08

Your boiler's outside temperature sensor is sending an incorrect signal or has lost connection, meaning the system may not know how hard it needs to work to heat your home.

Low Engineer only £90-160

Parts commonly replaced

  • External temperature sensor
  • Sensor wiring

Related codes

Full explanation for E08
Showing 11–20 of 29
E10

Your boiler has switched itself off because it has detected an issue with the sensor that monitors the temperature of the exhaust gases.

High Engineer only £120-220

Parts commonly replaced

  • Flue Gas NTC Sensor
  • Heat Exchanger cleaning
  • Wiring harness

Related codes

Full explanation for E10
E14

Your boiler is failing to recognise that the flame has lit correctly, causing the system to shut down for safety.

High DIY-safe £100-280

What to check first

  1. Check if other gas appliances in your home, like a gas hob, are working to ensure gas is reaching the property
  2. Check that your prepaid gas meter has credit, if applicable
  3. Press the Reset button on the boiler control panel and hold for five seconds

Parts commonly replaced

  • Flame detection electrode
  • Ignition lead
  • Gas valve

Related codes

Full explanation for E14
E21

Your boiler has shut down because the waste water pipe that carries away condensation is blocked or frozen, causing water to back up into the unit.

High DIY-safe £80-140

What to check first

  1. Locate the plastic white pipe exiting the wall outside your property.
  2. If the weather is freezing, pour warm (not boiling) water over the external pipe to melt any ice blockages.
  3. Check that the end of the pipe is not submerged in water or blocked by debris.
  4. Reset the boiler using the control knob to see if the error clears.

Parts commonly replaced

  • Condensate trap
  • Condensate discharge pipework
  • Internal electrode (if water damaged)

Related codes

Full explanation for E21
Er01+RESET

Your boiler has failed to light the flame, which has caused it to shut down for safety purposes.

High DIY-safe £100-£350

What to check first

  1. Check if other gas appliances in your home, like the hob, are working to ensure gas supply is active.
  2. Check your gas meter to ensure it has credit if you use a prepay meter.
  3. Press and hold the 'RESET' button for five seconds to see if the boiler restarts.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Printed Circuit Board (PCB)
Full explanation for Er01+RESET
Er02+RESET

Your boiler has shut down because it has detected an internal temperature that is too high, often caused by a blockage or a pump failure.

High DIY-safe £100-£280

What to check first

  1. Press and hold the 'RESET' button for a few seconds to see if the boiler restarts.
  2. Check that all radiator valves are fully open to allow water to flow.
  3. Ensure your boiler pressure is between 1.0 and 1.5 bar on the pressure gauge.

Parts commonly replaced

  • Overheat Thermostat
  • Circulation Pump
  • Main Heat Exchanger (Descaling)
Full explanation for Er02+RESET
Er03+RESET

Your boiler has detected a general internal fault that has caused the system to lock out for safety.

High DIY-safe £100-280

What to check first

  1. Press and hold the 'Reset' button for 5 seconds to clear the temporary error
  2. Check that your electricity supply is stable and the boiler fuse hasn't tripped
  3. Ensure there is credit on your gas meter (if applicable)

Parts commonly replaced

  • PCB (Main Circuit Board)
  • Ignition Electrode
  • Flame Sensing Probe
Full explanation for Er03+RESET
Er04+

Your boiler has detected that there is not enough water pressure or the water isn't moving through the system properly to operate safely.

High DIY-safe £100-£280

What to check first

  1. Check the pressure gauge on the front of the boiler; it should be between 1 and 1.5 bar.
  2. If the pressure is too low, use the filling loop valves underneath the boiler to top it up.
  3. Ensure all radiator valves and isolation valves are fully open.
  4. Restart the boiler using the reset button once the pressure is corrected.

Parts commonly replaced

  • Circulation pump
  • Water pressure switch
  • Primary heat exchanger
Full explanation for Er04+
Er05+

Your boiler has stopped working because the internal fan, which safely clears exhaust fumes, is not running at the correct speed or has lost communication with the main control board.

High Engineer only £180-£350

Parts commonly replaced

  • Extraction Fan
  • Main PCB (Printed Circuit Board)
  • Venturi Tube
Full explanation for Er05+
Er06+

Your boiler has lost track of the radiator water temperature due to a faulty internal sensor, causing the system to stop running as a safety precaution.

High Engineer only £90-160

Parts commonly replaced

  • Central heating NTC thermistor
  • NTC wiring harness
Full explanation for Er06+
Er07+

Your boiler's hot water sensor has failed, meaning it cannot accurately measure or control the temperature of the water coming out of your taps.

Medium Engineer only £90-160

Parts commonly replaced

  • Domestic Hot Water (DHW) NTC thermistor probe
  • Wiring harness
Full explanation for Er07+
Showing 21–29 of 29
Er08+

Your boiler's outside temperature sensor has developed a fault or is sending incorrect data, which might stop the heating from adjusting correctly to the weather.

Low Engineer only £90-160

Parts commonly replaced

  • External temperature probe (NTC)
  • Sensor wiring harness
Full explanation for Er08+
Er09+

Your boiler has detected that a sensor monitoring the temperature of the exhaust gases is not working correctly, causing the system to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • Flue Temperature Probe (NTC)
  • Wiring Harness
Full explanation for Er09+
Er10+RESET

Your boiler has shut down because a sensor has detected that the exhaust gases are becoming dangerously hot.

Emergency Engineer only £120-280

Parts commonly replaced

  • Flue NTC sensor
  • Main Heat Exchanger
  • Burner gasket
Full explanation for Er10+RESET
Er11+RESET

Your boiler detects a flame when it shouldn't be there, so it has shut down as a safety precaution.

High Engineer only £120-300

Parts commonly replaced

  • Ionisation electrode
  • Gas valve
  • Main PCB
Full explanation for Er11+RESET
Er14+

Your boiler has sensed that water is not moving through the system properly or is overheating too quickly, causing it to shut down for 10 minutes to protect itself.

High DIY-safe £120-350

What to check first

  1. Check the pressure gauge and top up to 1.5 bar if it is too low
  2. Ensure all radiator valves and isolation valves under the boiler are fully open
  3. Bleed your radiators to remove any trapped air pockets

Parts commonly replaced

  • Circulation Pump
  • Flow Switch
  • Primary Heat Exchanger (Cleaning/Descaling)
Full explanation for Er14+
Er14+RESET

Your boiler has shut down because it is overheating or water is not circulating through the system properly.

High DIY-safe £180-450

What to check first

  1. Check that your central heating valves (lockshields) are open
  2. Ensure your radiator valves are turned to the highest setting
  3. Check the boiler pressure gauge and top up to 1.5 bar if it is low
  4. Press the Reset button once to see if the fault clears

Parts commonly replaced

  • Circulating Pump
  • Primary Heat Exchanger
  • Overheat Thermostat
Full explanation for Er14+RESET
Er99

Your boiler has lost its configuration settings or isn't receiving power correctly, meaning it doesn't know which specific model it is supposed to be.

High Engineer only £100-£350

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Control Panel Interface
Full explanation for Er99
Li01

Your boiler has shut down because the internal water temperature has become too hot while trying to provide hot water.

High DIY-safe £100-280

What to check first

  1. Check that the radiator valves and the main boiler valves are fully open
  2. Ensure the central heating system pressure is between 1.0 and 1.5 bar
  3. Reset the boiler using the control knob to see if the fault clears

Parts commonly replaced

  • DHW Temperature Sensor (NTC)
  • Plate Heat Exchanger
  • Circulation Pump
Full explanation for Li01
lock-out

Your boiler has switched itself off because it has detected that it is getting too hot or there is a problem with the exhaust temperature.

High DIY-safe £90-280

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure is between 1 and 1.5 bar on the gauge
  3. Press the 'Reset' button on the front control panel and hold for 2-5 seconds

Parts commonly replaced

  • Safety Thermostat (Overheat Stat)
  • Flue Temperature Probe
  • Circulation Pump
Full explanation for lock-out