Ideal Logic Max Combi 2 Fault codes & diagnostics

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

Combi Natural Gas 2022-present
Download the Ideal Logic Max Combi 2 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

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Severity at a glance

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

All 17 documented codes

Tap any card for details

F 0C

Your boiler has detected a problem with the sensor that monitors the temperature of your hot water, which may prevent it from heating up correctly.

High Engineer only £90-160 Shared across the range

Parts commonly replaced

  • DHW Thermistor (NTC Sensor)
  • Wiring harness / Connector

Related codes

Full explanation for F 0C
F 01

Your boiler has stopped working because the water level inside the system is too low and needs to be topped up.

High DIY-safe £0-120 Shared across the range

What to check first

  1. Locate the filling loop handles (usually blue or black) underneath your boiler.
  2. Slowly turn both handles 90 degrees until you hear water entering the system.
  3. Watch the pressure gauge and close both handles once the needle reaches 1.5 bar.

Parts commonly replaced

  • Filling loop
  • Expansion vessel
  • Pressure sensor

Related codes

Full explanation for F 01
F 02

Your boiler has started an ignition process but the flame has unexpectedly gone out, causing the system to shut down for safety.

High DIY-safe £100-£350 Shared across the range

What to check first

  1. Check that your gas emergency control valve is open and you have credit on your gas meter.
  2. Try resetting the boiler by pressing the 'Restart' button on the front panel.
  3. Check if other gas appliances, like a cooker hob, are working to confirm gas supply is active.

Parts commonly replaced

  • Flame Sensing Electrode
  • Gas Valve
  • Ignition Lead
  • Spark Generator

Related codes

Full explanation for F 02
F 03

Your boiler has identified an issue with the part that clears waste gases, preventing the unit from lighting safely.

High Engineer only £280-450 Shared across the range

Parts commonly replaced

  • Fan motor
  • Main PCB
  • Wiring harness

Related codes

Full explanation for F 03
F 04

Your boiler is struggling to accurately measure the temperature of the water leaving the unit, which is preventing it from heating your home or water safely.

High Engineer only £100-£180 Shared across the range

Parts commonly replaced

  • Flow Thermistor (NTC Sensor)
  • Wiring Harness

Related codes

Full explanation for F 04
F 05

Your boiler is having trouble monitoring the temperature of the water returning from your radiators, which may cause it to run less efficiently or stop working intermittently.

Medium DIY-safe £90-160 Shared across the range

What to check first

  1. Press the Reset button on the front control panel
  2. Turn the boiler power off and back on at the fused spur switch
  3. Check that all radiator valves are open to ensure water is flowing back to the boiler correctly

Parts commonly replaced

  • Return Thermistor (NTC Sensor)
  • Wiring harness

Related codes

Full explanation for F 05
F 06

Your boiler has lost communication with the sensor that measures the temperature outside, meaning the heating may not adjust correctly to the weather.

Low Engineer only £90-180 Shared across the range

Parts commonly replaced

  • Weather Compensation Kit
  • Outdoor Sensor
  • Wiring harness

Related codes

Full explanation for F 06
F 07

Your boiler has stopped working because the electrical supply from your home to the unit is too low for it to operate safely.

High DIY-safe £0-120 Shared across the range

What to check first

  1. Check if there is a local power cut or if other appliances in the house are flickering.
  2. Ensure the boiler is plugged into a dedicated socket and not an extension lead.
  3. Restart the boiler using the reset button once you are sure the home's power supply is stable.

Parts commonly replaced

  • No parts usually required
  • Printed Circuit Board (PCB)

Related codes

Full explanation for F 07
F 09

Your boiler's internal computer brain is confused or having trouble talking to the gas components, meaning it has shut down for safety.

High Engineer only £180-450 Shared across the range

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Gas Valve

Related codes

Full explanation for F 09
L 0-

Your boiler has locked itself out because it has been manually reset too many times in a short period while trying to clear an underlying fault.

High DIY-safe £0-120 Shared across the range

What to check first

  1. Turn the boiler power off at the fused spur switch (the wall switch).
  2. Wait for at least five minutes to allow the internal timer to clear.
  3. Turn the power back on and see if a different primary fault code (such as F1 or L2) appears.

Parts commonly replaced

  • None (Reset limit reached)
  • Printed Circuit Board (PCB) if fault persists

Related codes

Full explanation for L 0-
L 0C

Your boiler thinks there is a flame present when it should be switched off, causing the system to shut down for safety.

High Engineer only £120-280 Shared across the range

Parts commonly replaced

  • Flame sensing electrode
  • Ignition lead
  • Printed Circuit Board (PCB)

Related codes

Full explanation for L 0C
L 01

Your boiler has switched itself off because it has detected it is getting too hot or there is not enough water moving through the system.

High DIY-safe £120-£350 Shared across the range

What to check first

  1. Check that your silver radiator valves (lockshields) are open and not turned off.
  2. Ensure your boiler pressure gauge is between 1 and 1.5 bar; top up using the filling loop if it is too low.
  3. Restart the boiler by pressing the ‘Reset’ button.

Parts commonly replaced

  • Pump
  • Flow Temperature Sensor
  • Heat Exchanger (de-sludging)

Related codes

Full explanation for L 01
L 02

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

High DIY-safe £120-350 Shared across the range

What to check first

  1. Check that your gas pre-payment meter (if you have one) has credit.
  2. Verify that other gas appliances, like a hob, are working to ensure gas is flowing to the property.
  3. Hold the 'Reset' button for three seconds to clear the fault and restart the ignition sequence.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Flame Sensing Probe
  • Spark Leads

Related codes

Full explanation for L 02
L 04

Your boiler has stopped working because it cannot accurately measure the temperature of the water leaving the unit.

High Engineer only £90-160 Shared across the range

Parts commonly replaced

  • Flow Thermistor (NTC Sensor)
  • Wiring Harness
  • Main PCB

Related codes

Full explanation for L 04
L 05

Your boiler has sensed a problem with the sensor that monitors the water temperature returning to the unit, causing it to stop working for safety.

High Engineer only £120-190 Shared across the range

Parts commonly replaced

  • Return Thermistor (NTC Sensor)
  • Wiring Harness

Related codes

Full explanation for L 05
L 06

Your boiler has shut down because it cannot safely get rid of exhaust fumes or waste water, often due to a blockage in the outside pipes.

High DIY-safe £60-180 Shared across the range

What to check first

  1. Check the white plastic condensate pipe outside for signs of ice or debris.
  2. If frozen, gently pour warm (not boiling) water over the pipe to melt the blockage.
  3. Restart the boiler by pressing the 'Reset' button.

Parts commonly replaced

  • Condensate trap
  • Flue pressure switch
  • Fan

Related codes

Full explanation for L 06
L 09

Your boiler has encountered a computer or electronic communication error and has locked itself out for safety.

High Engineer only £250-550 Shared across the range

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Gas Valve
  • Wiring Loom

Related codes

Full explanation for L 09
Status & diagnostic codes

4 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

24 Diagnostic Your boiler is currently operating normally and is communicating its intended heating power level to the control system. 30 Diagnostic Your boiler is displaying a technical configuration code indicating it is not correctly communicating its intended heating power to the system. 35 Diagnostic Your boiler is undergoing a routine internal self-check to confirm it is operating at its correct heating power level, which is a normal part of its software cycle. U Diagnostic Your boiler is currently in a manual service mode used for filling or venting the system and will not operate normally until this mode is exited.
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