No Communication with Hot Swap Terminal Unit

What does E4-9770 mean?

Communication with the hot swap terminal unit has been lost. This can be due to a temporary glitch or a hardware failure in the terminal unit or its communication path, affecting all I/O modules connected to it. This can lead to loss of I/O control.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Verify the power supply to the terminal unit.

2. 4

   If the error persists after a restart and checks, replace the hot swap terminal unit.