Appendix A: Troubleshooting Communication Data Issues
Symptom or Error
PLC Communication
4. Is the “PLC Ok” LED on?
In Fault
If the “PLC Ok” LED is off, there is a problem with either the MPU11 or
GPIO4D board.
5. Does your MPU11 have the updated crystal installed?
MPU11 boards that shipped prior to ##### may need to have the
crystal replaced due to a manufacturing defect
in the crystal. If your
MPU11 is dated prior to ##### (see pic) return it for repair.
