Viessmann Vitodens 333 Service Instructions Manual page 76

Troubleshooting
Fault codes
(cont.)
Display Const. Weath.
fault comp.
code
CF X
dA X
db X
dd X
dE X
E4 X X
76
System char- Cause
acteristics
Control mode Communica-
tion fault
LON com-
munication
module
Control mode Room tem-
without room perature
influence sensor, heat-
ing circuit A1
shorted out
Control mode Room tem-
without room perature
influence sensor, heat-
ing circuit
M2 shorted
out
Control mode Room tem-
without room perature
influence sensor, heat-
ing circuit A1
lead broken
Control mode Room tem-
without room perature
influence sensor, heat-
ing circuit
M2 lead bro-
ken
Burner Fault
blocked ply voltage
24 V
Remedy
Replace the LON
communication
module
Check the room
temperature sen-
sor heating cir-
cuit A1
Check the room
temperature sen-
sor heating cir-
cuit M2
Check the room
temperature sen-
sor, heating cir-
cuit A1 and the
remote control
DIP switch set-
tings (see
page 105)
Check the room
temperature sen-
sor, heating cir-
cuit M2 and the
remote control
DIP switch set-
tings (see
page 105)
sup- Replace the con-
trol unit