MELSEC iQ-F FX5 User’s Manual
The MELSEC iQ-F FX5 series PLC provides high-speed processing, reliable control, and flexible expansion in a compact design.
It is suitable for industrial automation applications such as packaging, printing, converting, and general machinery.
Key Features
- Compact, integrated CPU design for easy installation
- High-speed instruction processing and fast I/O response
- Built-in diagnostics and protection functions
- Flexible control and communication with external devices
The FX5 series enables stable machine operation, efficient troubleshooting, and reliable system performance.
Find the Error Code List and Troubleshooting
1️⃣ Document Scope (IMPORTANT)
| Item | Coverage |
| PLC series | Mitsubishi MELSEC iQ-F (FX5U / FX5UC) |
| Based manuals | Hardware Manual (JY997D55301U) + Application Manual |
| Error source | CPU / Safety / Intelligent modules |
| Diagnostic tool | GX Works3 (mandatory) |
| Note | No single manual contains all error codes |
2️⃣ Error Severity Classification (Core Logic)
| Item | Coverage |
| PLC series | Mitsubishi MELSEC iQ-F (FX5U / FX5UC) |
| Based manuals | Hardware Manual (JY997D55301U) + Application Manual |
| Error source | CPU / Safety / Intelligent modules |
| Diagnostic tool | GX Works3 (mandatory) |
| Note | No single manual contains all error codes |
3️⃣ LED-Based First Diagnosis
| LED | Status | Meaning | Recommended Action |
| PWR | OFF | Power supply absent or unstable | Check 24 V DC supply, remove extension modules to isolate short or overload |
| BAT | Flashing | Battery voltage low | Replace battery, back up parameters and device data immediately |
| ERR | Flashing | Program or watchdog-related error | Check scan time, verify program and parameters, rewrite if necessary |
| ERR | ON (Solid) | Hardware or safety-related fault | Connect GX Works3 and read detailed diagnostics and event history |
| P.RUN | OFF | PLC stopped | Resolve error cause, reset CPU, then switch to RUN |
| P.RUN | Flashing | Online program change in progress | Wait until completion; do not power off during this state |
4️⃣ Explicit Error Codes in Hardware Manual
| Error Code | Related Module | Description | Root Cause | Corrective Action |
| 3052H | Safety Extension Module | Power-on sequence error | Safety extension module powered ON at incorrect timing |
Power ON order must be:
1) I/O & expansion modules 2) CPU module 3) Safety extension module |
5️⃣ Common FX5 CPU Error Codes (Field-Relevant)
| Error Code (Hex) | Error Type | Description | Typical Cause | Recommended Solution |
| 2100H | CPU Stop | Program execution error | Invalid instruction, corrupted logic | Correct ladder logic, recompile and download program |
| 2401H | CPU Stop | Parameter inconsistency | Parameter mismatch after modification | Re-download full parameter set and reset CPU |
| 4100H | CPU Stop | Watchdog timer timeout | Scan time exceeds watchdog limit | Optimize program, reduce cyclic load, adjust watchdog settings |
| 1900H | Moderate | Constant scan time error | Scan time limit violated | Adjust scan parameters or reduce task load |
| 3360H | Moderate | Nesting depth exceeded | Excessive nested loops or branches | Simplify logic structure, reduce nesting |
| 3400H | Moderate | Instruction operand error | Out-of-range or invalid operand | Verify instruction ranges and data types |
6️⃣ Watchdog Timer Error (Slitter-Specific)
| Item | Description |
| Error code | 4100H (Watchdog timeout) |
| Detection logic | Actual scan time exceeds watchdog limit |
| Related registers | SD524 / SD525 (maximum scan time) |
| PLC reaction | CPU enters STOP state |
7️⃣ Battery Error (Often Ignored, Very Dangerous)
| Item | Description |
| Indicator | BAT LED flashing |
| Special relay | SM8005 (battery voltage low) |
| Special register | SD8005 (actual battery voltage) |
| Protected data | Latched devices, clock data, retained parameters |
8️⃣ Intelligent / Analog Module Errors (Typical)
| Error Code | Module Type | Description | Typical Cause | Corrective Action |
| 1A80H | Analog Input | Input range setting error | Range parameter outside allowed limits | Correct input range and re-download parameters |
| 1A90H | Analog Module | Offset / gain setting error | Calibration value out of range | Re-calibrate module and verify sensor specs |
| 3081H | Analog / Intelligent | External power supply failure | 24 V DC auxiliary supply lost | Restore power supply and verify wiring |
| 1BB0H | Analog Input | Wire break detection | Sensor cable disconnected or damaged | Repair wiring or replace sensor |
9️⃣ I/O Troubleshooting
| Symptom | Confirming Method | Root Cause | Recommended Solution |
| Output does not turn ON | Force output ON in GX Works3 | Wiring error, duplicate SET/RST, interlock logic | Correct wiring, review ladder logic, remove duplicate control |
| Output does not turn OFF | Stop PLC and observe output state | Short circuit, welded relay, logic error | Fix wiring, replace output module if still ON |
| Input does not turn ON | Short input terminal to 24 V / 0 V | Incorrect S/S wiring, faulty sensor | Correct common wiring, replace sensor |
| Input does not turn OFF | Measure leakage current | Leakage current > 1.5 mA | Add bleeder resistor, change sensor type |
| Input flickering | Monitor input status online | Noise, poor grounding, long cables | Improve shielding, separate power/signal wiring |
Still Struggling? Let Our Experts Assist You
Facing persistent machine issues? Our team of technical experts is here to help. At Jota Machinery, we provide tailored solutions and ongoing support to keep your production running smoothly—no matter the challenge.