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Troubleshooting Racks and Units Section 11-3
11-3 Troubleshooting Racks and Units
CPU Racks and Standard Expansion Racks
Special I/O Units
Refer to the Operation Manual for the Special I/O Unit to troubleshoot any
other errors.
Symptom Cause Remedy
POWER indicator is not lit. PCB short-circuited or damaged. Replace Power Supply Unit.
(1) Error in program. Correct program
(2) Power line is faulty. Replace Power Supply Unit.
RUN output* does not turn ON.
RUN indicator lit.
(*CJ1W-PA205R)
Internal circuitry of Power Supply Unit
is faulty.
Replace Power Supply Unit.
Serial Communications Unit or CPU
Bus Unit does not operate or malfunc-
tions.
(1) The I/O Connecting Cable is faulty.
(2) The I/O bus is faulty.
Replace the I/O Connecting Cable
Replace the I/O Control Unit or I/O
Interface Unit.
Bits do not operate past a certain point.
Error occurs in units of 8 points.
I/O bit turns ON
All bits in one Unit do not turn ON.
Symptom Cause Remedy
The ERH and RUN
indicators on the Spe-
cial I/O Unit are lit.
I/O refreshing is not being performed for the
Unit from the CPU Unit (CPU Unit monitoring
error).
It’s possible that cyclic refreshing has been dis-
abled for the Special I/O Unit in the Cyclic
Refresh Disable Setting in the PLC Setup (i.e.,
the bit corresponding to the unit number has
been set to 1).
Change the bit corresponding to the unit num-
ber to 0 to enable cyclic refreshing, or make
sure that the Unit is refreshed from the program
using IORF or FIORF (CJ1-H-R CPU Units
only) at least once every 11 s.
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