BoilerFaultCodes 5v[0
Parameter error
Main MainEco Fault codes & diagnostics
61 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
CombiSystem Natural GasLPG 15-35 kW 2006 onwards Discontinued
Replaced by: Baxi 600 or 800 Series
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The fault code is already on your display
Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →
Severity at a glance
Each cell = one fault code. Hover to identify. 61 Unrated
Just want the most common Main MainEco faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 61 documented codes
Tap any card for details
5v[1
Maximum flow temperature exceeded
5v[2
Maximum increase of the flow temperature has been exceeded
5v[7
Maximum difference between the flow and return temperature exceeded
5v[10
Shutdown input is open
5v[11
Shutdown input active or frost protection active
5v[12
Communication error with the HMI PCB
5v[13
Communication error with the SCU PCB
5v[15
Gas pressure too low
5v[16
Configuration error
Showing 11–20 of 61
5v[17
Configuration fault or default parameter table incorrect
5v[18
Configuration error (Boiler/PSU not recognised)
5v[19
Configuration fault or parameters df-dV unknown
5v[20
Configuration procedure active
5v[21
Communication fault
5v[22
No flame during operation
5v[25
Internal fault in gas/air unit
Code A
Maintenance message
Code B
Blockage
Code C
Shutdown input
Showing 21–30 of 61
Communication fault
Blockage
e[00
Parameter error
e[01
Parameter error
e[02
Sensor fault, temperature fault or flow fault
e[03
Sensor fault, temperature fault or flow fault
e[04
Sensor fault, temperature fault or flow fault
e[05
Sensor fault, temperature fault or flow fault
e[06
Sensor fault, temperature fault or flow fault
e[07
Sensor fault, temperature fault or flow fault
e[08
Sensor fault, temperature fault or flow fault
Showing 31–40 of 61
e[09
Sensor fault, temperature fault or flow fault
e10
Difference between the flow and return temperatures too great
e11
Sensor fault, temperature fault or flow fault
e12
Temperature of heat exchanger above normal range (high-limit thermostat STB)
e14
burner start-up failures
e16
False flame signal
e17
Problem on the gas valve
e34
Fan fault
e35
Sensor fault, temperature fault or flow fault
e36
Ignition fault
Showing 41–50 of 61
e37
Communication fault
e38
Communication error with the SCU PCB
e39
Shutdown input in locked-out mode
e40
HRU/URC unit test error
e41
Maximum temperature of heat exchanger or control unit exceeded
Error code 1
Sensor fault, temperature fault or flow fault
Error code 2
Maximum temperature of heat exchanger or control unit exceeded
Error code 3
Ignition fault: 5 burner start-up failures
Error code 4
Fan fault
Error code 5
Parameter error
Showing 51–60 of 61
Error code 6
Miscellaneous
Fan fault
Repair
Flame loss
Blockage
Ignition fault
Repair
Miscellaneous
Blockage
Overheat temperature protection
Repair
Parameter error
Blockage
Reinitialisation
Repair
Resetting...
Repair
Sensor error
Repair (Flashing red signal)
Showing 61–61 of 61
Temperature protection
Blockage (Flashing green signal)