Hello,
Back in December 2017, we replaced a customer's PLC-5 control system with a CompactLogix. Everything was working fine until about a month ago, when they started having an I/O fault, Code 16 - I/O module connection failed on required module. At first it was showing up on multiple modules, and also the end cap. However, after a few more faults, it was only showing up on module 2. We replaced that module and the faults stopped for about a week and then returned. The module we replaced is a 1769-IA16.
Any idea what may be causing this? The customer insists nothing was done to the panel since the initial installation.