WAGO 750 Series Manual page 117

Fault code 3: "Internal bus protocol fault"
Fault argument
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
Fault description
- Internal bus communication
malfunction; faulty device can't
be detected
Fieldbus Controller 750-841
LED Display
Trouble shooting
If the fieldbus node comprises
internal system supply modules
(750-613), make sure first that the
power supply of these modules is
functioning. This is indicated by
the status LEDs. If all I/O modules
are connected correctly or if the
fieldbus node doesn't comprise
750-613 modules you can detect
the faulty I/O module as follows:
turn off the power supply of the
node. Place the end module in the
middle of the fieldbus node. Turn
the power supply on again.
– If the LED is still blinking, turn
off the power supply and place the
end module in the middle of the
first half of the node (towards the
coupler).
– If the LED doesn't blink, turn off
the power supply and place the end
module in the middle of the second
half of the node (away from the
coupler).
Turn the power supply on again.
Repeat this procedure until the
faulty I/O module is detected.
Replace the faulty I/O module. If
there is only one I/O module left
but the LED is still blinking, then
this I/O module or the coupler is
defective. Replace defective
component.
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