Atag E Range Fault codes & diagnostics

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

CombiSystem Natural Gas 24-38 kW 2013-2018 Discontinued
GC Numbers 41-310-1241-310-1347-310-1347-310-14

Replaced by: iC Series

Download the Atag E Range manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

This boiler uses LED flash patterns

Count the flashes in one repeating group before the pause. That number is your fault code. Do not reset until you have noted it. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.
1 Emergency 42 High 6 Medium
Just want the most common Atag E Range faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 49 documented codes

Tap any card for details

LED / flash-pattern codes
FILL (flashing)

Your boiler has lost water pressure and needs to be topped up to work at full capacity correctly.

Medium DIY-safe

What to check first

  1. Locate the external filling loop, usually a silver braided hose with one or two valves located underneath the boiler.
  2. Slowly open the valve(s) to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.
  3. Close the valve(s) tightly and check for any leaks around the connection points.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
Full explanation for FILL (flashing)
flashing FILL / HIGH

Your boiler's water pressure has dropped too low, which is preventing it from working at its full heating capacity.

High DIY-safe

What to check first

  1. Locate the external filling loop, which is a silver braided hose connecting two pipes near your boiler.
  2. Open the valves at both ends of the hose slowly to allow water into the system.
  3. Watch the pressure gauge on the front of the boiler until the needle reaches 1.5 bar, then turn both valves firmly off.

Parts commonly replaced

  • Filling loop
  • Pressure gauge
  • Expansion vessel
Full explanation for flashing FILL / HIGH
Digital codes
00

Your boiler is struggling to ignite or maintain a stable flame, meaning it cannot provide you with heating or hot water.

High Engineer only £150-300

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe

Related codes

Full explanation for 00
01

Your boiler has detected an electrical fault in its internal control system that is preventing it from operating safely.

High Engineer only £150-300

Parts commonly replaced

  • Main control board
  • Wiring harness
  • External sensor wiring

Related codes

Full explanation for 01
02

Your boiler is trying to ignite but cannot establish a flame, meaning it currently cannot provide heating or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe

Related codes

Full explanation for 02
04

Your boiler's computer is experiencing a general internal error, meaning it has safely shut itself down to prevent potential damage.

High Engineer only £150-300

Parts commonly replaced

  • Control PCB
  • Wiring harness
  • Main ignition transformer

Related codes

Full explanation for 04
05

Your boiler's internal computer has encountered a critical electronic failure and can no longer safely control the heating or hot water functions.

High Engineer only £300-600

Parts commonly replaced

  • Main Control PCB
  • Wiring harness

Related codes

Full explanation for 05
10

Your boiler has stopped working because one of its internal sensors is sending incorrect information to the control system.

High Engineer only £120-220

Parts commonly replaced

  • Flow temperature sensor
  • Return temperature sensor
  • Wiring harness

Related codes

Full explanation for 10
12

Your boiler has stopped working because an internal safety fuse that powers its control system has blown.

High Engineer only £120-250

Parts commonly replaced

  • 3AT internal fuse
  • Control PCB

Related codes

Full explanation for 12
13

Your boiler has experienced an internal computer error that is preventing it from starting up correctly.

High DIY-safe £250-500

What to check first

  1. Locate the Reset button on the control panel
  2. Press and hold the Reset button for 2-3 seconds
  3. Wait for the boiler to complete its restart sequence

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Control Panel Interface

Related codes

Full explanation for 13
Showing 11–20 of 49
14

Your boiler has encountered a computer processing error that is preventing it from starting up correctly.

High Engineer only £250-£450

Parts commonly replaced

  • Main PCB (Control Board)

Related codes

Full explanation for 14
15

Your boiler has encountered a computer or electronic processing fault that is preventing it from running safely.

High Engineer only £250-550

Parts commonly replaced

  • Main PCB (Control Board)
  • Wiring Harness

Related codes

Full explanation for 15
16

Your boiler has encountered a computer or electronic processing fault that is preventing it from heating your home.

High Engineer only £250-550

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring harness

Related codes

Full explanation for 16
17

Your boiler has encountered a computer or communication error within its main control board, preventing it from running safely.

High DIY-safe £250-450

What to check first

  1. Switch the boiler off at the fused spur switch or main power supply.
  2. Wait for 30 seconds.
  3. Switch the power back on and press the 'Reset' button on the control panel.

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring harness
Full explanation for 17
18

Your boiler has shut down because the water inside the unit has reached a temperature that is too hot to operate safely.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves (TRVs) are turned to the highest setting
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Wait 30 minutes for the unit to cool down and then press the Reset button

Parts commonly replaced

  • Circulation Pump
  • NTC Temperature Sensor
  • Main Heat Exchanger (Flushing)

Related codes

Full explanation for 18
19

Your boiler's main computer has encountered an internal error and has stopped working to prevent any potential damage.

High Engineer only £250-500

Parts commonly replaced

  • Main PCB
  • Control board wiring loom

Related codes

Full explanation for 19
20

Your boiler's internal computer has encountered a software or hardware conflict and has stopped working as a safety precaution.

High DIY-safe £250-550

What to check first

  1. Locate the 'Reset' button on the boiler control panel
  2. Press and hold the button for 2-3 seconds
  3. Wait to see if the error clears and the boiler restarts

Parts commonly replaced

  • Main PCB (Printed Circuit Board)
  • Wiring Loom

Related codes

Full explanation for 20
24

Your boiler's internal computer brain has detected a software or communication error and has stopped working to protect itself.

High DIY-safe £250-550

What to check first

  1. Switch the boiler off at the fused spur or power switch.
  2. Wait for 30 seconds.
  3. Switch the power back on and press the 'Reset' button.

Parts commonly replaced

  • Main PCB (Control Board)
  • Display PCB

Related codes

Full explanation for 24
28

Your boiler has stopped working because the internal fan, which safely pushes exhaust gases out of your home, is not spinning or communicating with the main control board.

High Engineer only £280-450

Parts commonly replaced

  • Fan assembly
  • Main PCB
  • Wiring harness
Full explanation for 28
30

Your boiler has detected that water is not circulating through the system properly, causing a large temperature gap between the water leaving and returning to the unit.

High DIY-safe £120-£350

What to check first

  1. Check that all radiator valves and boiler isolation valves are fully open.
  2. Ensure the system pressure is between 1.0 and 1.5 bar on the pressure gauge.
  3. Bleed all radiators to remove trapped air that might be blocking water flow.
  4. Restart the boiler by pressing the reset button.

Parts commonly replaced

  • Circulation pump
  • Flow and return thermistors
  • Central heating filter (cleaning/replacement)

Related codes

Full explanation for 30
Showing 21–30 of 49
31

Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of the water leaving the unit, preventing it from heating safely.

High Engineer only £120-190

Parts commonly replaced

  • Flow temperature sensor (NTC)
  • Wiring harness
  • Control PCB

Related codes

Full explanation for 31
32

Your boiler has detected a fault with the pipe that measures the temperature of the water returning to the unit, causing it to stop running for safety.

High Engineer only £120-£200

Parts commonly replaced

  • Return water temperature sensor (NTC)
  • Wiring harness / Cable connections

Related codes

Full explanation for 32
34

Your boiler has stopped working because it cannot get a temperature reading from the pipe that returns water back into the unit.

High Engineer only £90-160

Parts commonly replaced

  • Return water temperature sensor (NTC)
  • Wiring harness
  • Control PCB

Related codes

Full explanation for 34
35

Your boiler's internal computer has encountered a software or communication glitch and needs to be restarted.

High DIY-safe £180-450

What to check first

  1. Press the Reset button on the control panel
  2. Turn the boiler power off at the fused spur switch for 30 seconds
  3. Turn the power back on and wait for the boiler to restart

Parts commonly replaced

  • Main Printed Circuit Board (PCB)
  • Display Control Unit

Related codes

Full explanation for 35
36

Your boiler's computer brain has encountered a confused internal signal and has stopped working as a safety precaution.

High DIY-safe £180-350

What to check first

  1. Locate the Reset button on the control panel
  2. Press and hold the Reset button for 2-3 seconds
  3. Wait for the boiler to restart and check if the code clears

Parts commonly replaced

  • Main PCB (Control Board)
  • Display PCB
Full explanation for 36
60

Your boiler's computer has detected an internal configuration error regarding how much power it is allowed to use, meaning it cannot safely operate until the settings are corrected.

High Engineer only £120-250

Parts commonly replaced

  • Control PCB

Related codes

Full explanation for 60
67

Your boiler has detected an unusual temperature difference between its internal pipes while it is turned off, causing it to pause operations as a safety precaution.

Medium Engineer only £150-250

Parts commonly replaced

  • Flow sensor
  • Return sensor
  • Control board

Related codes

Full explanation for 67
80

Your boiler has automatically turned itself off because the exhaust fumes leaving the unit have become dangerously hot.

Emergency Engineer only £150-350

Parts commonly replaced

  • Flue gas temperature sensor
  • Heat exchanger
  • Primary flow switch

Related codes

Full explanation for 80
81

Your boiler has detected that a crucial internal temperature sensor has become unplugged or disconnected, so it has safely shut itself down to prevent operation until it is fixed.

High Engineer only £120-220

Parts commonly replaced

  • Flue gas sensor
  • Wiring harness

Related codes

Full explanation for 81
82

Your boiler has detected a faulty sensor reading in the exhaust system and has switched itself off to stay safe, meaning you currently have no heating or hot water.

High Engineer only £150-250

Parts commonly replaced

  • Flue gas sensor
  • Wiring harness

Related codes

Full explanation for 82
Showing 31–40 of 49
85

Your boiler is struggling to detect water moving through the system and is currently running an automated self-check to clear any trapped air.

Medium Engineer only £120-250

Parts commonly replaced

  • Central heating pump
  • Flow sensor
  • System bypass valve

Related codes

Full explanation for 85
86

Your boiler has detected that the electricity coming from your home's wall socket is unstable, meaning it cannot operate safely and has shut itself down.

High Engineer only £120-250

Parts commonly replaced

  • Electrical supply wiring
  • Boiler control board (PCB)

Related codes

Full explanation for 86
Block 60

Your boiler’s internal computer has lost its correct settings for how much power it should be using, causing it to stop运行 to prevent damage.

High Engineer only £120-250

Parts commonly replaced

  • Control PCB
  • Gas Valve
Full explanation for Block 60
Block 67

Your boiler has detected an unusual temperature difference while it is supposed to be switched off, and it is pausing its operations until the system temperatures balance out.

Medium Engineer only £120-250

Parts commonly replaced

  • Flow/Return Temperature Sensor
  • Central Heating Pump
Full explanation for Block 67
Block 80

Your boiler has detected that the exhaust gases are becoming dangerously hot and has shut itself down to prevent internal damage.

High Engineer only £150-350

Parts commonly replaced

  • Heat exchanger
  • Flue gas temperature sensor
  • Burner assembly

Related codes

Full explanation for Block 80
Block 81

Your boiler has stopped working because it cannot detect a safety component that monitors exhaust fumes, which prevents it from firing up.

High Engineer only £120-250

Parts commonly replaced

  • Flue gas sensor
  • Wiring harness
  • PCB

Related codes

Full explanation for Block 81
Block 82

Your boiler has detected an electrical fault in its safety monitoring system and has automatically shut down to keep you safe.

High Engineer only £150-250

Parts commonly replaced

  • Flue gas sensor
  • Wiring harness

Related codes

Full explanation for Block 82
Block 85

Your boiler is struggling to detect the water flowing through it, so it has paused operation to run an automatic air-removal process to clear any trapped bubbles.

High Engineer only £120-250

Parts commonly replaced

  • Flow sensor
  • Circulating pump

Related codes

Full explanation for Block 85
Block 86

Your boiler has detected that the electricity supply coming into your home is unstable or fluctuating outside of normal limits.

Medium Engineer only

Parts commonly replaced

  • Control PCB
  • Power supply surge protection fuse

Related codes

Full explanation for Block 86
Error 00

Your boiler is failing to light the internal burner correctly, meaning it cannot produce heat or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Flame rectification probe
Full explanation for Error 00
Showing 41–49 of 49
Error 01

Your boiler has detected an electrical fault in its internal control circuit, which has caused it to shut down to prevent further damage.

High Engineer only £150-300

Parts commonly replaced

  • Control PCB
  • Wiring harness
  • External pump or diverter valve

Related codes

Full explanation for Error 01
Error 02

Your boiler is failing to light the internal flame needed to produce heat or hot water.

High Engineer only £150-350

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Ignition lead
Full explanation for Error 02
Error 04

Your boiler has detected an unstable power supply or a sudden electrical disruption, causing it to shut down for safety reasons.

High Engineer only £120-250

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Wiring harness
Full explanation for Error 04
Error 05

Your boiler's main computer brain is experiencing a critical error and can no longer safely operate the heating system.

High Engineer only £250-450

Parts commonly replaced

  • Control Unit/PCB
Full explanation for Error 05
Error 12

Your boiler has stopped working because an internal safety fuse responsible for the control power has blown, preventing the system from starting.

High Engineer only £120-220

Parts commonly replaced

  • 3AT internal fuse
  • Control PCB

Related codes

Full explanation for Error 12
Error 19

Your boiler has detected that the water returning to it is far too hot, causing it to shut down to prevent damage to the system.

High Engineer only £150-350

Parts commonly replaced

  • Return temperature sensor
  • Central heating pump
  • Plate heat exchanger

Related codes

Full explanation for Error 19
Error 28

Your boiler has switched itself off because it cannot detect that the internal fan, which is essential for clearing exhaust gases, is spinning correctly.

High Engineer only £200-350

Parts commonly replaced

  • Fan assembly
  • Wiring harness
  • Printed Circuit Board (PCB)
Full explanation for Error 28
FILL

Your boiler has lost water pressure and needs to be topped up to work at full capacity.

Medium DIY-safe

What to check first

  1. Locate the filling loop (a silver flexi-hose) underneath the boiler or near your pipework.
  2. Open the valves on the filling loop to allow cold mains water to enter the system.
  3. Watch the pressure gauge on the boiler until the needle reaches the green zone (typically 1.2 to 1.5 bar).
  4. Close both valves tightly and remove the filling loop if required by your specific model.

Parts commonly replaced

  • Filling loop
  • Pressure relief valve
  • Pressure sensor
Full explanation for FILL
HIGH

Your boiler has automatically shut down because the internal water pressure has climbed too high to operate safely.

High DIY-safe

What to check first

  1. Locate a radiator in your home with a bleed valve.
  2. Place a cloth or small container under the valve.
  3. Open the bleed valve slowly to release water until the pressure gauge on your boiler drops to between 1.0 and 1.5 bar, then close the valve tightly.

Parts commonly replaced

  • Pressure relief valve
  • Filling loop
  • Pressure sensor
Full explanation for HIGH
Status & diagnostic codes

3 operating states & engineer diagnostics

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

Err.L Diagnostic Your boiler is displaying a stored history of previous faults, which acts like a diagnostic log rather than a current problem. Err.L - Err.5 Diagnostic Your boiler is displaying a stored history of previous faults, which means it is currently reporting that it has encountered technical issues in the past. STOP Status Your boiler is telling you that the internal water pressure has successfully returned to the correct level after you topped it up.