Ariston E-System ONE Fault codes & diagnostics

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

System Natural Gas 2020-present
GC Numbers 41-116-4741-116-48
Download the Ariston E-System ONE 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.
1 Emergency 10 High 4 Medium
Just want the most common Ariston E-System ONE faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 15 documented codes

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1P4

Your boiler has detected that water is not flowing through the heating system as efficiently as it should, so it has stopped working to prevent overheating.

High DIY-safe £120-250

What to check first

  1. Check all radiator valves in your home are fully open.
  2. Check your boiler pressure gauge; if it is below 1 bar, top it up using the filling loop.
  3. Restart the boiler by pressing the reset button.

Parts commonly replaced

  • Circulation pump
  • System filter
  • Flow sensor

Related codes

Full explanation for 1P4
3 05

Your boiler's internal computer is experiencing a communication error, which means it cannot operate safely and has shut down.

High Engineer only £250-450

Parts commonly replaced

  • Main PCB
  • Wiring harness

Related codes

Full explanation for 3 05
3 06

Your boiler's internal computer is experiencing a communication error and has shut down to prevent potential system damage.

High Engineer only £250-450

Parts commonly replaced

  • Main Printed Circuit Board (PCB)

Related codes

Full explanation for 3 06
6 10

Your boiler has detected that it is running much hotter than it should be and has shut itself down to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Primary Heat Exchanger
  • Central Heating Pump

Related codes

Full explanation for 6 10
7 11

Your boiler is struggling to accurately read the temperature of the water returning from your heating system, which is preventing it from running your heating correctly.

Medium Engineer only £120-220

Parts commonly replaced

  • Return NTC sensor
  • Wiring harness

Related codes

Full explanation for 7 11
7 12

Your boiler is having trouble reading the temperature in one of the secondary heating zones, which may prevent that part of your home from heating up properly.

Medium Engineer only £120-200

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

Full explanation for 7 12
7 13

Your boiler is having trouble communicating with one of the temperature sensors for your heating system, which may cause your heating or hot water to work inconsistently or stop altogether.

Medium Engineer only £120-220

Parts commonly replaced

  • NTC Temperature Sensor
  • Wiring harness

Related codes

Full explanation for 7 13
7 23

Your boiler has detected that the water temperature in one specific heating area of your home has risen higher than it should be.

Medium Engineer only £120-250

Parts commonly replaced

  • NTC Temperature Sensor
  • Zone Valve
  • Main PCB

Related codes

Full explanation for 7 23
107

Your boiler has stopped working because the water returning from your radiators is significantly hotter than the water being sent out, suggesting a blockage or a pump problem is preventing proper circulation.

High DIY-safe £120-£350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the central heating system pressure is between 1 and 1.5 bar on the gauge
  3. Gently bleed your radiators to remove any trapped air
  4. Restart the boiler using the Reset button

Parts commonly replaced

  • Circulation Pump
  • Main Heat Exchanger (cleaning or replacement)
  • Flow/Return Thermistors

Related codes

Full explanation for 107
108

Your boiler has lost water pressure and has shut down to prevent damage, meaning it simply needs to be refilled to the correct level.

High DIY-safe £0-120

What to check first

  1. Locate the filling loop (usually blue handles or a small plastic key) underneath the boiler.
  2. Slowly open the valves until you hear water entering the system.
  3. Watch the pressure gauge and close the valves tightly once it reaches 1.5 bar.
  4. The error code should clear automatically; if not, press the 'Reset' button.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Auto air vent

Related codes

Full explanation for 108
109

Your boiler has too much water pressure inside the system, causing it to shut down for safety.

Emergency DIY-safe £80-200

What to check first

  1. Check that the filling loop valves under the boiler are tightly closed.
  2. Bleed water from a radiator using a bleed key until the pressure gauge on the boiler falls back between 1 and 1.5 bar.
  3. Restart the boiler once the pressure is stabilised.

Parts commonly replaced

  • Filling loop valve
  • Expansion vessel
  • Pressure relief valve (PRV)

Related codes

Full explanation for 109
116

Your boiler has detected that the safety sensor for an underfloor heating circuit has tripped to prevent the floor from overheating.

High Engineer only £90-180

Parts commonly replaced

  • Floor thermostat
  • Overheat limit thermostat
  • Wiring harness

Related codes

Full explanation for 116
118

Your boiler has detected a fault with the sensor that measures the temperature of the water being sent to your radiators, which means it cannot heat your home safely.

High Engineer only £110-180

Parts commonly replaced

  • Central heating flow NTC sensor
  • Wiring harness
  • Main circuit board (PCB)

Related codes

Full explanation for 118
501

Your boiler has tried to light several times but has failed to create a flame, meaning you currently have no heating or hot water.

High DIY-safe £100-350

What to check first

  1. Check if your home gas supply is active by testing another gas appliance like a hob.
  2. Verify that your gas prepaid meter (if applicable) has enough credit.
  3. If it is freezing outside, check that the white plastic condensate waste pipe is not frozen.
  4. Hold the 'Reset' button for five seconds to see if the boiler restarts.

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Spark Generator

Related codes

Full explanation for 501
502

Your boiler thinks it sees a flame even though the gas should be turned off, so it has shut down as a safety precaution.

High Engineer only £140-£350

Parts commonly replaced

  • Ionisation Probe
  • Gas Valve
  • Main Control Board

Related codes

Full explanation for 502
Status & diagnostic codes

1 operating states & engineer diagnostics

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

3P9 Diagnostic Your boiler is simply reminding you that its annual safety check and service are now due.
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