LS Electric XGB/XGK — ERR LED & Error Log

LSIS · beginner · 20 min

An LS Electric XGB or XGK (XGT-series) PLC shows its health on the POWER/RUN/ERR/I-O LEDs, and it keeps a full error and warning log you can read in XG5000. Learn what a blinking ERR LED means and how to pull the current and previous errors.

ℹ️ On an LS Electric XGB/XGK, read the front LEDs first — POWER, RUN, ERR, I/O. A blinking ERR LED means the CPU logged a fault; the PLC keeps a full error/warning log you read in XG5000 (Online → error/warning).

Read the front LEDs

LS Electric XGB and XGK PLCs (the XGT series) put their status on the cover LEDs, and the troubleshooting manual gives recommended actions per LED state:

• POWER — supply present.
• RUN — the CPU is running; RUN/STOP LED OFF is a specific fault case to look up.
• ERR — a CPU error; a blinking ERR LED has its own troubleshooting section (the CPU detected a fault).
• I/O — module status; there's a dedicated case for I/O modules not working normally.

The cover LEDs get you to the right troubleshooting branch before you connect a laptop.

The PLC logs every error and warning

A real strength of the XGT platform: the PLC records every error and warning during operation. You don't have to catch it live — in XG5000 (the programming software), open Online → the 'error/warning' tab to check the current errors and the previous error log. That history is often what tells you a fault is intermittent and when it happens.

Error-handling flags (F area)

The XGK/XGB instruction set includes error-handling flags in the F area — special flags the CPU sets to indicate error conditions. Your program can read these to react to faults, and they're useful when diagnosing why the CPU went to STOP or flagged an error during Run.

Step-by-step

1. Read the LEDs — POWER/RUN/ERR/I-O — and go to the matching troubleshooting case (ERR blinking, RUN/STOP off, I/O not working).
2. Connect XG5000 and open Online → error/warning to read the current error and the previous error log.
3. Identify the fault from the logged code/description (program, I/O module, configuration, or power).
4. Fix the cause the log points to; for an I/O module fault, check/replace the flagged module.
5. Clear and confirm the ERR LED is off and RUN is steady; use the F-area flags in logic if you need the program to react.

Never do this

Don't just switch the CPU back to RUN after an ERR without reading the error/warning log — the log (and the F-area flags) tell you whether it was a one-off or a repeating fault. Fix the logged cause so it doesn't drop out again mid-production.