CompactLogix 1769-IF4’s OK light did not come one. The PLC went into IO fault with fault number 16#0312.
1769-IF4 has toggle switch in the circuit board to select power from back plain or external power. If the switch is on external power and it does not receive 24VDC, it throws this error. You can switch the power select back to “Bus”. Or you can connect external power to it.
If this does not fix your problem, you may have a damaged card.