Ideal Logic Code COMBI2 38 Fault codes & diagnostics

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

Combi Natural Gas 2022-present
GC Number 47-387-20
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Severity at a glance

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

All 16 documented codes

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BCC Activation Fault

Your boiler's internal computer chip and the control board are having trouble communicating, which has caused the system to stop working for safety.

High Engineer only £120-350 Shared across the Logic Code range

Parts commonly replaced

  • Boiler Chip Card (BCC)
  • Printed Circuit Board (PCB)

Related codes

Full explanation for BCC Activation Fault
BCC Fault

Your boiler's internal computer has lost its 'identity' or connection to its configuration card, meaning it cannot safely command the heating or hot water to turn on.

High Engineer only £140-300 Shared across the Logic Code range

Parts commonly replaced

  • Boiler Chip Card (BCC)
  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for BCC Fault
c0

Your boiler has detected an internal issue and is prompting you to perform a manual reset to see if it can clear the error and restart successfully.

Medium DIY-safe Shared across the Logic Code range

What to check first

  1. Locate the Reset button on the front control panel
  2. Press and hold the button for 3 to 5 seconds
  3. Wait for the boiler to cycle and check if the code clears and the burner ignites

Parts commonly replaced

  • Main PCB
  • Wiring harness
  • Ignition lead

Related codes

Full explanation for c0
c2

Your boiler's electronic brain is unable to read its internal configuration card, meaning it cannot operate safely or reliably.

High Engineer only £150-250 Shared across the Logic Code range

Parts commonly replaced

  • Boiler Chip Card (BCC)
  • Main Control PCB

Related codes

Full explanation for c2
False Flame Lockout

Your boiler thinks it sees a flame when there shouldn't be one, which is a safety feature that has caused the system to shut down.

High Engineer only £120-£350 Shared across the Logic Code range

Parts commonly replaced

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

Related codes

Full explanation for False Flame Lockout
Fan Fault

Your boiler has detected an issue with the electrical fan that clears exhaust gases, preventing it from starting up for safety reasons.

High Engineer only £250-£450 Shared across the Logic Code range

Parts commonly replaced

  • Fan Assembly
  • Main Printed Circuit Board (PCB)
  • Wiring Harness

Related codes

Full explanation for Fan Fault
Flame Loss

Your boiler has stopped working because the flame has gone out unexpectedly, often due to a temporary interruption in your gas supply or a sensor issue.

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

What to check first

  1. Check if other gas appliances, like a hob, are working to confirm gas is reaching the property.
  2. If you have a prepay meter, ensure you have credit and the valve is open.
  3. Press the 'Restart' button on the boiler control panel once to see if the flame re-establishes.

Parts commonly replaced

  • Ionisation Probe
  • Spark Electrode
  • Gas Valve

Related codes

Full explanation for Flame Loss
Flow Temperature Overheat

Your boiler has become too hot and has shut itself down as a safety precaution to prevent damage.

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

What to check first

  1. Check the pressure gauge is between 1 and 1.5 bar and top up if it is too low
  2. Ensure all radiator valves and the boiler isolation valves are fully open
  3. Bleed your radiators to remove any trapped air pockets
  4. Reset the boiler using the control knob or reset button

Parts commonly replaced

  • Central heating pump
  • Flow thermistor
  • Main heat exchanger

Related codes

Full explanation for Flow Temperature Overheat
Flow Thermistor

Your boiler has lost its ability to measure the temperature of the water leaving the unit, which has caused it to stop working for safety.

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

Parts commonly replaced

  • Flow Thermistor (NTC Sensor)
  • Wiring Harness

Related codes

Full explanation for Flow Thermistor
L1

Your boiler has detected that the water inside it has become dangerously hot and has shut itself down to prevent damage.

High Engineer only £120-250 Shared across the Logic Code range

Parts commonly replaced

  • NTC thermistor
  • Primary heat exchanger
  • Pump

Related codes

Full explanation for L1
Low Mains Voltage

Your boiler is not receiving enough electrical power from your home's supply to operate safely and has shut down to protect its internal parts.

High Engineer only £100-350 Shared across the Logic Code range

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Mains electrical wiring

Related codes

Full explanation for Low Mains Voltage
Low Water Pressure

Your boiler has stopped working because the water pressure inside the system has dropped too low, which is usually easy to fix by topping it up.

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

What to check first

  1. Locate the filling loop (usually a silver flexible hose with one or two blue lever valves) underneath the boiler.
  2. Open the valve(s) slowly until you hear water running and watch the pressure gauge needle rise.
  3. Close the valves tightly once the gauge reaches 1.5 bar and check if the boiler restarts.

Parts commonly replaced

  • Filling loop hose
  • Expansion vessel re-pressurisation
  • Pressure relief valve (PRV)

Related codes

Full explanation for Low Water Pressure
No Water Flow

Your boiler is unable to flow water or gas properly and has stopped working to prevent damage.

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

What to check first

  1. Check that your gas emergency control valve is in the 'on' position
  2. If you have a prepay meter, check that you have enough credit
  3. Reset the boiler by turning the control knob to 'RE' and back to 'on'

Parts commonly replaced

  • Gas Valve
  • Pump
  • Flow Sensor

Related codes

Full explanation for No Water Flow
No Water Flow Thermistor

Your boiler has detected that water isn't moving through the system properly or a temperature sensor has failed, preventing it from heating your home safely.

High Engineer only £120-£280 Shared across the Logic Code range

Parts commonly replaced

  • Flow Thermistor (NTC Sensor)
  • Internal Pump
  • Main Heat Exchanger

Related codes

Full explanation for No Water Flow Thermistor
Outside Sensor Fault

Your boiler has lost connection to the sensor that measures the temperature outside, which may cause your heating to be less efficient or unresponsive.

Low DIY-safe £90-160 Shared across the Logic Code range

What to check first

  1. Press the Reset button on the boiler control panel.
  2. Check for any obvious damage to the thin wiring leading to the sensor on your external wall.
  3. Ensure the sensor is not covered by debris or overgrown garden plants.

Parts commonly replaced

  • Outside weather compensation sensor
  • Wiring harness

Related codes

Full explanation for Outside Sensor Fault
Return Thermistor

Your boiler's internal sensor that monitors the temperature of the water returning to the unit has stopped working correctly, causing the system to shutdown for safety.

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

Parts commonly replaced

  • Return Thermistor (NTC Sensor)
  • Wiring Harness

Related codes

Full explanation for Return Thermistor
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