Lists of fault diagnostics
(Original Document)
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At a Glance
The messages displayed on the diagnostics screens are used to assist in debugging the project. These messages must be concise and are sometimes ambiguous (as different faults may have the same consequences).
These diagnostics are on two levels: module and channel, the latter being the most explicit. The lists below show the message headings with suggestions for finding out what is wrong.
List of the module fault messages
The table below provides a list of the module fault messages.
Fault indicated
Possible interpretation and/or action
Module failure
The module has a fault.
Check the module mounting. Change the module.
Faulty channel(s)
One or more channels have a fault.
Refer to channel diagnostics.
Self-test
The module is running a self-test. Wait until the self-test is complete.
Note: For Modicon M340, if the Xbus line termination are missing, the module will stay in this state.
Different hardware and software configurations
There is a lack of compatibility between the module configured and the module in the rack.
Make the configuration and the software configuration compatible.
Module is missing or off
Install the module. Fasten the mounting screws.
List of channel fault messages
The table below gives the list of fault messages at channel level.
Fault indicated. Other consequences.
Possible interpretation and/or action.
External fault or counting input fault:
  • encoder or proximity sensor supply fault,
  • line break or short circuit of at least one encoder differential signal (1A, 1B or 1Z),
  • SSI series frame fault,
  • specific fault on absolute encoder.
Outputs are set to 0 in automatic mode.
Invalid measurement message.
Check the sensor connections.
Check the sensor power supply.
Check the sensor operation.
Delete the fault and acknowledge if the fault storing is configured (CTY 2C).
Counting pulses or incremental encoder: preset or reset to acknowledge the Invalid measurement message.
Counting application fault:
  • measurement overrun
  • overspeed
Outputs are set to 0 in automatic mode.
Invalid measurement message.
Diagnose the fault more precisely (external causes).
Check the application again, if necessary.
Delete the fault and acknowledge if the fault storing is configured (CTY 2C).
Counting pulses or incremental encoder: preset or reset to acknowledge the Invalid measurement message.
Auxiliary input/output fault:
  • power supply
  • short circuit of at least one output
Outputs are set to 0 in automatic mode.
Check the output connections.
Check the input/output power supply (24V).
Diagnose the fault more precisely (external causes).
Delete the fault and acknowledge if the fault storing is configured (CTY 2C).
Internal fault or channel self-test:
  • faulty module,
  • module missing or off,
  • module running self-test.
Module fault has gone down to channel level.
Refer to module level diagnostics.
Different hardware and software configurations
Module fault has gone down to channel level.
Refer to module level diagnostics.
Invalid software configuration:
  • incorrect constant
  • bit combination not associated with any configuration
Check and modify the configuration constants.
Communication fault
Check the connections between the racks.
Application fault: refusal to configure or adjust
Diagnose the fault more precisely.