Ideal Logic+ COMBI2 C30 Fault codes & diagnostics

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

Combi Natural Gas 2022-present
GC Number 47-387-01
Download the Ideal Logic+ COMBI2 C30 manualThe official installation and service manual (PDF), the document these fault codes were read from. PDF

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Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 11 High 2 Medium 1 Low
Fault codes

All 15 documented codes

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4.2

Your boiler has shut down because its internal temperature has become too high, often caused by a lack of water flow or a blockage.

High DIY-safe £100-350

What to check first

  1. Check that your boiler pressure is between 1 and 1.5 bar on the gauge
  2. Ensure all radiator valves and the isolation valves under the boiler are fully open
  3. Press the 'Restart' button on the front control panel

Parts commonly replaced

  • Circulation Pump
  • Overheat Thermostat
  • Main Heat Exchanger

Related codes

Full explanation for 4.2
4.3

Your boiler has failed to light after several attempts, meaning it has shut down as a safety precaution and will not provide heating or hot water.

High DIY-safe £100-£350

What to check first

  1. Check if other gas appliances in your home, such as a gas hob, are working to ensure gas is reaching the property.
  2. Ensure your pre-payment gas meter has credit if applicable.
  3. Press the 'Reset' button on the boiler control panel once to see if it restarts. Only attempt this three times maximum.
  4. If it is freezing outside, check that your white plastic condensate pipe leading outdoors is not frozen and blocked.

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame sensing probe
  • PCB (Printed Circuit Board)

Related codes

Full explanation for 4.3
4.4

Your boiler has detected a flame when it shouldn't be there, which usually means a internal component is stuck open or there is a fault with the electronics.

Emergency Engineer only £180-350

Parts commonly replaced

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

Related codes

Full explanation for 4.4
4.5

Your boiler has detected that the water pressure inside the system is too low to run safely and has switched itself off.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually blue-handled levers) underneath the boiler.
  2. Slowly open the valves until you hear water entering the system.
  3. Watch the pressure gauge and close the valves when the needle reaches 1.5 bar.
  4. Restart the boiler if it does not reset automatically.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for 4.5
4.6

Your boiler is struggling to keep its flame lit, which means the system has safely shut down to prevent issues.

High DIY-safe £120-£350

What to check first

  1. Check that your gas credit hasn't run out if you have a prepayment meter
  2. Ensure other gas appliances like your hob are working to confirm your gas supply is active
  3. Check that the white plastic condensate pipe outside hasn't frozen in cold weather
  4. Press the 'Reset' button on the boiler display

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Gas valve
  • Spark generator

Related codes

Full explanation for 4.6
4.7

Your boiler has stopped working because the internal fan, which safely clears exhaust fumes, is not running correctly.

High Engineer only £280-450

Parts commonly replaced

  • Fan Assembly
  • Main PCB
  • Wiring Loom

Related codes

Full explanation for 4.7
4.8

Your boiler has detected an issue with the sensor that monitors the temperature of the water leaving the unit, preventing it from heating your home safely.

High Engineer only £90-160

Parts commonly replaced

  • Flow thermistor (NTC sensor)
  • Wiring harness / connector
  • Printed Circuit Board (PCB)

Related codes

Full explanation for 4.8
4.9

Your boiler has detected an issue with the sensor that monitors the temperature of the water returning to the unit, likely causing it to shut down for safety.

High Engineer only £90-160

Parts commonly replaced

  • Return Thermistor (NTC Sensor)
  • Wiring harness
  • Main PCB

Related codes

Full explanation for 4.9
4.10

Your boiler has lost communication with the sensor that monitors the outdoor temperature, which means it cannot automatically adjust its settings based on the weather.

Low Engineer only £90-180

Parts commonly replaced

  • Outside weather compensation sensor
  • Sensor wiring harness

Related codes

Full explanation for 4.10
4.11

Your boiler is currently unable to provide heating to your radiators, although your hot water taps will continue to work as normal.

Medium Engineer only £150-300

Parts commonly replaced

  • Diverter Valve
  • Central Heating Sensor
  • PCB

Related codes

Full explanation for 4.11
4.12

Your heating is working normally, but your boiler is not currently producing any hot water when you turn on the taps.

Medium Engineer only £100-£250

Parts commonly replaced

  • DHW Flow Sensor
  • Diverter Valve

Related codes

Full explanation for 4.12
4.13

Your boiler has lost power or the screen has failed, meaning it will not operate and you cannot see any settings or status messages.

High DIY-safe £100-350

What to check first

  1. Check if other appliances in the house are working to rule out a general power cut
  2. Check your home's main fuse box (consumer unit) to see if a circuit has tripped
  3. Ensure the boiler's power switch (usually a fused spur near the unit) is turned on

Parts commonly replaced

  • Display PCB
  • Main Control PCB
  • Internal Fuse
Full explanation for 4.13
4.14

Your boiler is having trouble measuring the temperature of your hot water, so it has temporarily stopped producing it to keep you safe.

High Engineer only £90-160

Parts commonly replaced

  • DHW NTC Thermistor
  • Wiring harness

Related codes

Full explanation for 4.14
Ignition Lockout

Your boiler has temporarily stopped working because it tried to start up five times without successfully catching a flame.

High DIY-safe £90-250

What to check first

  1. Check that your gas supply is turned on and other gas appliances like the cooker are working
  2. Check if your gas prepayment meter has run out of credit
  3. Press the reset button on the front of the boiler for up to 5 seconds to try restarting it

Parts commonly replaced

  • Ignition lead
  • Spark electrode
  • Gas valve

Related codes

Full explanation for Ignition Lockout
Too Many Restarts

Your boiler has temporarily locked itself out because it tried to restart itself too many times in a short period.

High Engineer only £100-£250

Parts commonly replaced

  • PCB
  • Gas Valve
  • Ignition Electrode

Related codes

Full explanation for Too Many Restarts
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