liminfoMitsubishi Error Code Reference
Mitsubishi PLC & servo error code reference with causes and solutions
About Mitsubishi Error Code Reference
The Mitsubishi PLC & Servo Error Code Reference is a free, searchable database of over 40 error codes for Mitsubishi MELSEC iQ-R, iQ-F, and Q-series PLCs along with MR-J series servo amplifier alarms. It covers 5 major categories: CPU & System errors (1000-series: WDT timeout, RAM/ROM failure, hardware faults, battery alarms, division-by-zero, BCD conversion errors, parameter errors), Communication errors (2400-series: CC-Link timeout, station duplication, MELSECNET/H, Ethernet timeout, IP conflict, serial RS-232/422, CC-Link IE Field, SLMP, GX Works connection), Positioning module alarms (3000-series: parameter, stroke limits, emergency stop, dog signal, completion timeout), MR-J servo amplifier alarms (AL.10 undervoltage through AL.51 excessive position deviation), and I/O Module diagnostics (4000-series: input/output hardware, analog calibration, thermocouple burnout, RTD wire break, high-speed counter, D/A conversion, remote I/O).
Each error code entry provides the specific error number or alarm code, a clear description of the fault condition, root cause analysis, and numbered step-by-step troubleshooting procedures. The reference includes GX Works2/GX Works3 diagnostic procedures, MR Configurator2 parameter checks, cable and hardware inspection steps, and parameter adjustment recommendations.
Designed for automation engineers, PLC programmers, maintenance technicians, and control system integrators working with Mitsubishi Electric factory automation equipment in manufacturing plants, packaging lines, semiconductor fabs, and material handling systems.
Key Features
- CPU & System error codes (1000-2010): WDT timeout, RAM/ROM failure, hardware error, battery alarm, fuse blown, division-by-zero, BCD conversion, parameter error
- Communication fault codes (2400-2460): CC-Link timeout and station duplication, MELSECNET/H, Ethernet timeout and IP conflict, RS-232/422 serial, CC-Link IE Field, SLMP, GX Works USB/Ethernet connection
- Positioning module alarms (3000-3050): parameter error, software/hardware stroke limits, emergency stop, near-point dog signal, positioning complete timeout
- MR-J servo amplifier alarms: AL.10 undervoltage, AL.16 encoder error, AL.20 overcurrent, AL.24/25 overload, AL.32 overvoltage, AL.37 parameter error, AL.46 motor overtemperature, AL.51 excessive position deviation
- I/O module diagnostics (4000-4050): input/output hardware errors, analog calibration, thermocouple burnout, RTD wire break, high-speed counter, D/A conversion, remote I/O no response
- Step-by-step troubleshooting with GX Works2/GX Works3 and MR Configurator2 procedures
- Instant search by error code number (1000, AL.16) or keyword (communication, encoder, overload)
- Bilingual Korean/English for international maintenance teams
Frequently Asked Questions
What Mitsubishi PLC error code ranges are covered?
The reference covers: 1000-series for CPU & System errors (WDT, memory, hardware, battery, arithmetic, parameters), 2400-series for Communication errors (CC-Link, MELSECNET/H, Ethernet, serial, CC-Link IE Field, SLMP, GX Works connection), 3000-series for Positioning module alarms (parameters, stroke limits, emergency stop, home return), 4000-series for I/O module errors (digital I/O, analog calibration, thermocouple/RTD, counter, D/A conversion, remote I/O), plus MR-J servo amplifier AL alarm codes.
How do I troubleshoot MR-J servo alarm AL.16 encoder error?
AL.16 indicates an encoder feedback signal abnormality on MR-J servo amplifiers. Step-by-step: (1) Check and reseat the encoder cable at CN2 connector. (2) Inspect connector pins for damage or bending. (3) Verify cable shield grounding. (4) Confirm encoder cable length is within the 30-meter maximum specification. (5) In electrically noisy environments, enhance cable shielding or reroute away from power cables. (6) If the alarm persists after cable replacement, replace the motor/encoder assembly.
What causes Mitsubishi PLC error 1000 WDT timeout?
Error 1000 occurs when the CPU scan time exceeds the watchdog timer setting (default 200ms). Common causes: excessively long program loops, infinite loops in ladder logic, or too many timer/counter operations. To resolve: (1) Check the program in GX Works for infinite loops. (2) Increase the WDT value in CPU parameters if the program legitimately requires longer scan time. (3) Split large programs into smaller blocks. (4) Optimize timer and counter usage to reduce scan time.
How do I fix CC-Link communication timeout error 2400?
Error 2400 means the CC-Link master received no response from a slave station. Troubleshooting: (1) Check CC-Link cable physical connections at all stations. (2) Verify 110-ohm terminating resistors are installed at both ends of the network. (3) Confirm each station number is unique and correctly assigned. (4) Verify all stations use the same communication speed setting. (5) Check the CC-Link module LED indicators for specific fault indications. Common root causes are loose cables, missing terminators, and duplicate station numbers.
What does MR-J servo alarm AL.32 overvoltage mean?
AL.32 indicates the DC bus voltage in the servo amplifier main circuit has exceeded the upper threshold. This typically occurs during rapid deceleration when regenerative energy from the motor exceeds the regenerative resistor capacity. Resolution: (1) Verify input power voltage is within specification. (2) Confirm the MR-RB regenerative resistor option is properly installed. (3) Check the regenerative load ratio monitor value. (4) Extend deceleration time to reduce regenerative energy. (5) Consider upgrading to a higher-capacity regenerative resistor or adding a regenerative converter for high-inertia applications.
How do I resolve positioning module error 3050 completion timeout?
Error 3050 means positioning did not complete within the configured timeout period. Causes include servo amplifier alarms preventing motion, mechanical interference or binding, and in-position signal not being received. Steps: (1) Check the servo amplifier for active alarms (AL codes). (2) Inspect for mechanical interference, jamming, or excessive load. (3) Verify the in-position (INP) signal range setting matches the required positioning accuracy. (4) Consider extending the timeout duration parameter. (5) Verify acceleration/deceleration times and travel distance are appropriate for the mechanical system.
What should I check for thermocouple burnout error 4020?
Error 4020 indicates the thermocouple input module detected an open circuit (burnout condition). This means the thermocouple wire is broken or disconnected. Steps: (1) Check thermocouple wiring for breaks or loose connections at terminal blocks. (2) Reseat thermocouple connectors on the input module. (3) Measure thermocouple resistance with a multimeter to confirm wire continuity. (4) Verify the thermocouple type setting (K, J, T, etc.) matches the actual sensor. (5) Replace the thermocouple if resistance measurement confirms an open circuit.
How do I connect to a Mitsubishi PLC when getting GX Works error 2460?
Error 2460 indicates GX Works2 or GX Works3 cannot establish communication with the PLC. For USB connection: (1) Check the USB cable is firmly connected. (2) Reinstall the USB communication driver. (3) Try a different USB port. (4) Verify the CPU type in GX Works matches the physical module. For Ethernet connection: (1) Confirm the PLC IP address and port number. (2) Check the LAN cable and verify the LINK LED is lit. (3) Ensure no firewall is blocking the communication port. (4) Reconfigure the connection destination settings in GX Works (Online > Connection Destination).