NAiS FP Series Hardware Manual page 150

FP0 Hardware
Check of input condition (input indicator LEDs are ON)
<Procedure >
Monitor the input condition using a programming tool.
If the input monitored is OFF, there is probably an abnormality in the FP0's input
circuit. Please contact your dealer.
If the input monitored is ON, check the program again.
Also, check the leakage current at the input devices (e.g., two-wire type sensor)
and check for the duplicated use of output or the program flow when a control in-
struction such as MC or JP is used.
Check the settings of the I/O allocation.
Matsushita Electric Works (Europe) AG
11.2 Troubleshooting
11-7