Publication 1769-UM002B-EN-P - July 2005
Module Diagnostics and Troubleshooting 5-3
Power-up Diagnostics
At module power-up, a series of internal diagnostic tests are performed. These
diagnostic tests must be successfully completed or the module status LED
remains off and a module error results and is reported to the controller.
Channel Diagnostics
When an input or output module channel is enabled, the module performs a
diagnostic check to see that the channel has been properly configured. In
addition, the module checks each channel on every scan for configuration
errors, over-range and under-range, open-circuit (input module in 4 to 20 mA
range only) and output wire broken/high load resistance (output module only)
conditions.
Out-of-Range Detection (Input and O
utput Modul
es)
For input modules, whenever the data received at the channel word is out of
the defined operating range, an over-range or under-range error is indicated in
the Input Data file.
For output modules, whenever the controller is driving data over or under the
defined operating range, an over-range or under-range error is indicated in the
Input Data file.
Open-Circuit Detection (Input
Modules On
ly)
The module performs an open-circuit test on all enabled channels configured
for 4 to 20 mA inputs. Whenever an open-circuit condition occurs, the
under-range bit for that channel is set in the Input Data file.
Possible causes of an open circuit include:
• the sensing device may be broken
• a wire may be loose or cut
• the sensing device may not be installed on the configured channel
Table 5.1 Diagnostics
If module status
LED is:
Indicated
condition:
Corrective action:
On Proper
Operation
No action required.
Off Module Fault Cycle power. If condition persists, replace the
module. Call your local distributor or Rockwell
Automation for assistance.
Blinking
(1)
(1)
1769-OF8V and -OF8C only.
Isolated 24V
Power Not
Present
Check external power switch setting. Check wiring
to external power supply terminals. Check external
power supply.
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