BoilerFaultCodes F.000
The signal for the flow temperature sensor has been interrupted.
Vaillant ecoTEC plus 940 Fault codes & diagnostics
166 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.
Combi Gas 2023-present
GC Number 47-044-96
Download the Vaillant ecoTEC plus 940 manual
PDF
Versions & GC numbers
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. 166 Unrated
Which version do you have?
The GC number on your boiler's data badge identifies the exact appliance and production years, as recorded in the UK Product Characteristics Database.
| GC number | Appliance (register name) | Produced |
|---|---|---|
| 47-044-96 | ecoTEC plus 940 VUI 30/40CS/1-5 (N-GB) | 2023–present |
Appliance names and production years are taken from the UK Product Characteristics Database (the SAP/SEDBUK register). Where a GC number is also printed in this model's own manufacturer manual, both sources were checked to agree.
Just want the most common Vaillant ecoTEC plus 940 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes
All 166 documented codes
Tap any card for details
F.001
The signal for the return temperature sensor has been interrupted.
F.002
The signal for the domestic hot water connection temperature sensor has been interrupted.
F.003
The signal for the cylinder temperature sensor has been interrupted.
F.010
The flow temperature sensor has short-circuited.
F.011
The return temperature sensor has short-circuited.
F.012
The domestic hot water connection temperature sensor has short-circuited.
F.013
The cylinder temperature sensor has short-circuited.
F.020
The safety cut-out (SCO) interrupts the gas valve control. The gas valve was closed because the temperature of the flow or return temperature sensor has exceeded the maximum limit.
F.022
Operating limit filling pressure (≤ 0.03 MPa (≤ 0.30 bar))
Showing 11–20 of 166
F.023
The temperature spread between the flow/return is too great.
F.024
Thetemperatureincreasestoo quickly.
F.025
Thefluegastemperatureistoo high.
F.027
Aflamesignalhasbeendetec- tedwhiletheburnerisoff.
F.028
Condensate blockage
F.029
Condensate blockage
F.032
Thefanspeedisoutsideofthe tolerance.
F.035
Air/flue pipe blocked
F.040
The air ratio is too low.
F.042
The coding resistor (in the wiring harness) or the gas group resistor (on the PCB, if available) is invalid.
Showing 21–30 of 166
F.044
The ionisation signal for the control electrode is too low. The drift adaptation has failed.
F.047
The signal for the domestic hot water temperature sensor at the output for the internal cylinder is implausible.
F.049
The eBUS has short-circuited or two active eBUS sources have inverted polarity.
F.057
The combustion regulation has failed and the associated limp home mode has failed.
F.061
The ASIC or µControl does not run in the defined times.
F.062
The flame switch-off was detected after a delay.
F.063
EEPROM reports faults during the read/write test.
F.064
PCB fault
F.065
The permissible operating temperature range for an electronic component has been exceeded.
F.067
The flame monitor is defective.
Showing 31–40 of 166
F.068
The flame monitor reports an unstable signal.
F.070
The Device Specific Number (DSN) is incorrect, missing or does not match the coding resistor.
F.071
Flow temperature sensor returns implausible values.
F.072
The temperature spread between the flow and return temperature sensor is invalid.
F.074
The signal for the water pressure sensor has been interrupted.
F.075
The pressure change is too low when the heating pump is started up.
F.076
The overheating protection for the primary heat exchanger is active.
F.077
A condensate pump or an external flue non-return flap is blocking the burner operation.
F.078
The control centre is not supported by the unit.
F.080
The cold water inlet temperature sensor in the internal cylinder is defective.
Showing 41–50 of 166
F.081
Cylinder charging has failed.
F.083
When the burner starts, no temperature increase is registered at the flow or return temperature sensor or the temperature increase here is too slow.
F.084
The temperature difference between the flow and return temperature sensors return implausible values.
F.085
The NTC sensors are installed incorrectly.
F.087
The ignition transformer is not connected to the PCB.
F.088
The electrical connection to the gas valve has been interrupted.
F.089
The installed heating pump does not match the unit type.
F.090
Communication with the internal cylinder has been interrupted.
F.092
The gas-type conversion was not completed correctly.
F.095
The gas valve stepper motor has reached the minimum permissible step number.
Showing 51–60 of 166
F.096
The gas valve stepper motor has reached the maximum permissible step number.
F.097
The self-test of the main PCB has failed.
F.105
Offset for the gas valve assembly is missing
F.194
The power supply unit for the PCB is defective.
F.195
The unit has detected significant undervoltage in the power supply.
F.196
The unit has detected significant overvoltage in the power supply.
F.317
The signal for the volume flow sensor in the domestic hot water circuit is implausible.
F.318
The 3-port motorised valve does not move.
F.320
The heating pump is blocked. The unlocking function was not successful.
F.321
The pump electronics are defective.
Showing 61–70 of 166
F.322
The heating pump has overheated. The temperature could not be lowered by the limp home mode.
F.323
The heating pump is dry running.
F.324
The electrical connection to the pump has been interrupted.
F.325
The heating pump has a fault.
F.326
The hydraulics sensor and actuator test has detected at least two hydraulic components that are not working.
F.327
The minimum heating volume flow is limited due to there being no domestic hot water circuit connected.
F.330
The pump is not responding to commands during the hydraulic test.
F.334
The configuration of the flue system was not completed.
F.336
The unit is not permitted in this configuration.
F.337
The multiple-flue configuration conversion set is not suitable for the heat cell.
Showing 71–80 of 166
F.338
Incorrect multiple-flue configuration setting
F.342
The air-mass flow is not within the permitted limits.
F.343
The signal for the air-mass flow sensor is not plausible.
F.344
The control electrode can no longer be used.
F.347
Condensate blockage
F.363
The display's EEPROM reports errors during the read/write test.
F.707
No communication is possible between the display and the PCB.
F.905
Communication interface switched off
I.003
The product's maintenance time has been reached.
I.020
The water pressure in the heating system is at the lower limit.
Showing 81–90 of 166
I.144
The electrode drift test shows progressed ageing of the control electrode.
L.016
A flame loss has been detected at minimum output.
L.022
The circulation water volume in the heating circuit is too low.
L.025
The cold water inlet temperature sensor has short-circuited.
L.032
The volume flow sensor is defective or the signal is not plausible.
L.095
The gas valve stepper motor has reached the minimum permissible step number.
L.096
The gas valve stepper motor has reached the maximum
L.097
Theairratioistoolow.
L.105
Theunitisnotpurgedcorrectly.Thepurgeprogrammecouldnotbecompletedsuccessfully.
L.144
Theionisationsignalforthecontrolelectrodeistoolow.Thedriftadaptationhasfailed.
Showing 91–100 of 166
L.194
ThepowersupplyunitforthePCBisfaulty.
L.195
Theunithasdetectedundervoltageinthepowersupply.
L.196
Theunithasdetectedovervoltageinthepowersupply.
L.319
Theunit'sinternalbypassvalveisblocked.
L.320
Theheatingpumpisblocked.Theunitattemptstoloosentheblockage.
L.322
Thepumpelectronicshaveoverheated.
L.343
Thesignalfortheair-massflowsensorisnotplausible.
N.013
Thesignalforthewaterpressuresensorisinvalid.
N.027
Thesignalforthetemperature sensoronthedomestichotwa- terconnectionisimplausible.
N.032
Thevolumeflowsensoris defectiveorthesignalisnot plausible.
Showing 101–110 of 166
N.089
Theinstalledheatingpump doesnotmatchtheunittype.
N.095
Thegasvalvesteppermotor hasreachedtheminimumper- missiblestepnumber.
N.096
Thegasvalvesteppermotor hasreachedthemaximumper- missiblestepnumber.
N.097
Theairratioistoolow.
N.100
Thesignalfortheoutdoortem- peraturesensorhasbeeninter- rupted.
N.144
Theionisationsignalforthe controlelectrodeistoolow.The driftadaptationhasfailedagain.
N.194
The powersupplyunitforthe PCBisdefective.
N.270
Thetemperaturespreadvia thesecondaryheatexchanger (heatingflow–domestichot waterconnection)istoohigh. Theunitswitchesfromregulat- ingtocontrollinguntilthecause hasbeeneliminatedbycus- tomerservice.
N.317
Thesignalforthevolumeflow sensorinthedomestichotwa- tercircuitisimplausible.
N.319
Theunit'sinternalbypassvalve isblocked.
Showing 111–120 of 166
N.324
Theelectricalconnectiontothe pumphasbeeninterrupted.
N.343
Thesignalforthemassairflow sensorisnotplausible.Ifthe massairflowsensorsetiscon- nectedandthereisfeedback, butthevaluesareimplaus- ible,theunitworksinlimphome mode.
S.000
There is no demand for heating mode.
S.001
Heating mode is active and the fan is in prerun mode.
S.002
Heating mode is active and the heating pump is in prerun mode.
S.003
Heating mode is active and the unit ignites.
S.004
Heating mode is active and the burner is operating.
S.005
Heating mode is active and the heating pump and fan are in overrun mode.
S.006
Heating mode is active and the fan is in overrun mode.
S.007
Heating mode is active and the heating pump is in overrun mode.
Showing 121–130 of 166
S.008
Heating mode is active and the unit is in burner anti-cycling time.
S.009
The heating mode is active and the unit carries out an automatic drift adaptation of the control electrode in order to offset the ageing of the electrode.
S.010
The is no demand for domestic hot water draw-off.
S.011
The domestic hot water draw-off is active and the fan is starting up.
S.012
The domestic hot water draw-off is active and the heating pump is in prerun mode.
S.013
The domestic hot water draw-off is active and the unit ignites.
S.014
The domestic hot water draw-off is active and the burner is operating.
S.015
The domestic hot water draw-off is active and the heating pump and fan are in overrun mode.
S.016
The domestic hot water draw-off is active and the fan is in overrun mode.
S.017
The domestic hot water draw-off is active and the heating pump is in overrun mode.
Showing 131–140 of 166
S.019
Domestic hot water draw-off is active and the unit carries out an automatic drift adaptation of the control electrode in order to offset the ageing of the electrode.
S.020
There is no demand for the domestic hot water cylinder charging.
S.021
The domestic hot water cylinder charging is active and the fan starts.
S.022
The domestic hot water cylinder charging is active and the pump is in prerun mode.
S.023
The domestic hot water cylinder charging is active and the unit ignites.
S.024
The domestic hot water cylinder charging is active and the burner is operating.
S.025
The domestic hot water cylinder charging is active and the pump and fan are in overrun mode.
S.026
The domestic hot water cylinder charging is active and the fan is in overrun mode.
S.027
The domestic hot water cylinder charging is active and the heating pump is in overrun mode.
S.028
The domestic hot water cylinder charging is active and the unit is in burner anti-cycling time.
Showing 141–150 of 166
S.029
The domestic hot water cylinder charging is active and the unit carries out an automatic drift adaptation of the ionisation electrode in order to offset the ageing of the electrode.
S.030
No demand is present for the thermostat. Heating mode is blocked.
S.031
Heating mode has been deactivated and there is no domestic hot water demand.
S.032
The fan is restarted due to an excessive deviation in speed.
S.034
The frost protection function is active.
S.039
The floor surface-mounted thermostat or condensate pump blocks the burner operation. The unit is in awaiting period.
S.041
The water pressure in the heating system is too high.
S.042
An external unit (e.g. condensate pump or external flue non-return flap) is blocking the burner operation. The unit is in awaiting period.
S.054
Due to a water deficiency, the unit is in awaiting period.
S.057
The limphome mode for the combustion regulation blocks the burner operation. The unit is in awaiting period.
Showing 151–160 of 166
S.059
Heat demand available. The circulation water volume is not sufficient for a burner start.
S.088
The purge programme is active.
S.091
The presentation mode is active with limited functionality.
S.092
The self-test for the circulation water volume is active.
S.093
A flue gas analysis is not currently possible.
S.096
The self-test for the return temperature sensor is active. The heat demands are blocked.
S.097
The self-test for the water pressure sensor is active. The heat demands are blocked.
S.098
The self-test for the flow and return temperature sensor is active. The heat demands are blocked.
S.109
The standby mode is active.
S.175
The installation assistant is in progress and all demands are blocked.
Showing 161–166 of 166
S.199
The unit is automatically filled with water.
S.326
The hydraulics sensor and actuator test is active.
S.328
The external pump runs continuously and is not connected to the unit.
S.335
Checking whether a flue gas blockage is present.
S.341
The unit temporarily decreases the load to the minimum modulation due to long, permanent burner operation.
S.599
The unit has a fault.
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