CompactLogix 5370 T03:C16: I/O connection fault in Run mode, what to check?
I'm getting a Major Fault Type 3 Code 16 on my CompactLogix 5370 controller. It happens in Run mode, and the fault description points to an I/O connection failure on a required module. What should I check first?
A T03:C16 major fault on a Logix 5000 controller indicates that a connection to a required I/O module has failed while the controller was in Run mode. This fault occurs only if the module is configured to cause a major fault on the controller upon connection failure. The controller will set fault status bits associated with the module, and outputs will go to their configured fault state.
Likely causes and checks
1Module removed, unpowered, or failed
- Points to it
- The I/O module itself may have been physically removed, lost power, or experienced an internal failure. This is often indicated if only one module is named in the fault details and it appears dark or shows a fault status.
- Check
- Verify that the module is correctly seated in its chassis slot and that it is receiving power. Check the module's status indicators and review the Module Properties Connection tab in Studio 5000 Logix Designer for more details.
2Electronic keying mismatch after module replacement
- Points to it
- If an I/O module was recently replaced, there might be a mismatch between the installed module's catalog number or firmware and the electronic keying settings configured in the I/O configuration. The Connection tab in the module properties will typically report a keying or identity mismatch.
- Check
- Compare the catalog number and firmware version of the physically installed module with the I/O configuration in Studio 5000 Logix Designer, paying close attention to the electronic keying setting.
3Network path to remote I/O lost
- Points to it
- For remote I/O, the network path (e.g., EtherNet/IP, ControlNet) to the remote chassis, adapter, or switch may have been interrupted. This cause is suggested if multiple modules in the same remote chassis or rack lose their connection simultaneously.
- Check
- Inspect the network adapter, cabling, and switch ports involved in the communication path to the remote I/O. Also, check the communication module path within the I/O tree in Studio 5000 Logix Designer.
Next check: After checking the module's physical presence and power, and verifying electronic keying, examine the Major Faults tab in the controller properties for recent I/O fault information. If communication to the module is the issue, the Connection tab in the module's properties will be more useful than the Module Info tab.
Related questions
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