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Fault
code
Sub
code
Cause
Appliance
action
User action
E121
E2200 externalBus general
fault message
Bedienmodul
BM-2 and other
accessories do
not work.
Appliance is
working
Check wiring to accessories/ Bedienmodul BM-2
Check accessories/ Air Control and replace if defective
If there is still a fault after this: Take voltage from
appliance and replace basic pcb UWA2-B
E122
E2300 Internal ModBus fault;
general fault message
Appliance goes
to standby
Check wiring and connections to UWA2-B and the fans
Replace cable harness if damaged; Then exchange
UWA2B, exhaust fan and supply fan
E123
E2400 External ModBus fault;
general fault message
Operation via
Modbus does not
work
Check cabling of accessories; replace if damaged
Check accessories; replace if defective
If fault still occurs: Take voltage from appliance and
replace UWA2-B basic pcb
E124
E2500 USB port general fault
message
USB interface
not usable
Replace USB accessory
If the fault is not remedied after this: take the voltage from
the appliance and replace UWA2-B basic pcb
E170
E2600 One or more CO
2
sensor(en) defective;
general fault message
Appliance is
working; no CO
2
regulation
Check cabling and CO
2
sensor(s); replace if damaged
Check CO
2
sensor(s); replace if defective
E171
E2700 External preheater or
fuse defective; general
fault message
No preheater /
comfort control
responds
differently
Uncouple preheater and check preheater fuse; replace
fuse if defective
Has the fault not yet been remedied:
Replace external preheater
Put voltage back on appliance
Fault has automatically been reset
E172
E2800 External postheater or
fuse defective; general
fault message
No postheater /
comfort control
responds
differently
Uncouple postheater and check postheater fuse; replace
fuse if defective
Has the fault not yet been remedied:
Replace external postheater
Put voltage back on appliance
Fault has automatically been reset
Fault
xxxx
7100833_202010
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