GE Fanuc PLC Fault Codes: When to Repair or Replace

11/03/2026

by Qualitrol Support Team

If you're reading this, there's a good chance your line is down, a red light is staring back at you, and someone is asking when things will be running again. Take a breath. You're not on your own, and a fault light doesn't automatically mean an expensive fix.

This guide covers the most common fault lights and fault table messages on GE Fanuc (now GE-Emerson) Series 90-30, PACSystems RX3i and VersaMax PLCs. For each one, it explains what it usually means and what you can check yourself before you spend anything. If you'd rather talk it through with a person, call us at 1-704-702-6380. Our team has supported GE automation for more than 50 years, and we'll help you work out what's really wrong.

How to read GE PLC fault indicators

Before you pull a module or order anything, take a few minutes with the clues your PLC is already giving you. Many faults turn out to be a battery, a loose connection or a configuration issue, not a failed part. GE PLCs report problems in two places: the status LEDs on the hardware, and the fault tables in your programming software.

Look at the LEDs. The power supply or CPU shows overall health (power, OK, run, battery). Many I/O modules also have their own OK or field-power LEDs.
Open the PLC fault table. It logs CPU-level faults, such as configuration mismatches, battery warnings and program problems.
Open the I/O fault table. It lists module-level faults by rack and slot, so you can see exactly which module is reporting a problem.
Note the fault before you clear it. Write down or screenshot the fault description, rack, slot and time stamp. Clearing the table erases the evidence, and a fault that comes back after clearing is one of the clearest signs of failing hardware.

You'll view the fault tables in Logicmaster 90 (older Series 90-30 systems), VersaPro, or Proficy Machine Edition (newer systems, including RX3i).

Series 90-30 fault codes and LEDs (IC693 / IC694)

On a Series 90-30 system, the four LEDs on the rack power supply (such as the IC693PWR321 or IC693PWR322) are your first check.

What you see	What it usually means	Likely next step
PWR LED off	The power supply has no input power or has failed	Confirm incoming power. If power is present and PWR stays off, replace the power supply
OK LED off	The PLC has detected a problem; the CPU may have failed	Check the fault table. If OK stays off after a power cycle, suspect the CPU
OK LED blinking	A module may be faulty	Check the I/O fault table for the rack and slot
RUN LED off	The CPU is stopped (it does not report I/O failures)	Check the PLC fault table for the reason it stopped
BATT LED red	Memory backup battery voltage is too low to keep the program in RAM	Replace the battery (IC693ACC301) with power still on, and back up your program

Common Series 90-30 fault table messages

Loss of or Missing I/O Module: a configured module stopped responding. If it reappears after you reseat the module, or keeps coming back, the module or its rack slot is failing.
Addition of or Extra I/O Module: a module is present that isn't in the configuration. Seen alongside "Loss of" messages, it often points to a module dropping in and out intermittently.
System Configuration Mismatch: the hardware in the rack doesn't match the stored configuration. This stops the CPU. It often follows a module swap with the wrong part number or revision, or repeated intermittent module faults.
Low Battery Signal: the same warning as the red BATT LED. Act on it right away: if power is lost with a dead battery, the program can be wiped.
No User Program Present / No User Program on Power-up: memory was cleared, usually after a power loss with a failed battery. The CPU usually just needs the program reloaded from a backup; it isn't necessarily faulty.

If the BATT light comes back within weeks of a new battery, the battery usually isn't the problem. A weak power supply can drain it, so test or swap the supply.

PACSystems RX3i CPU status LEDs (IC695)

RX3i CPUs such as the IC695CPE302, CPE305 and CPE310 show their status on the CPU itself. Newer RX3i CPUs back up memory with an Energy Pack (such as the IC695ACC400) instead of a lithium battery. The table follows Emerson's CPE302/305/310 quick start guide (GFK-3249C); you'll find specs and replacement options on our IC695CPE305 product page.

What you see	What it means	Likely next step
OK off	No power, or the CPU has a problem	Confirm power. If OK stays off, the CPU may need repair or replacement
OK / RN blinking green	CPU is in Stop-Halt; possible watchdog timer fault	Check the fault tables. Repeated watchdog faults can point to a failing CPU
FLT solid red	CPU is in Stop/Faulted mode because of a fatal fault	Read the PLC fault table before clearing anything
EN off	Output scan is disabled	Outputs won't update. Check whether outputs were disabled on purpose
FRCE amber	An override is active on at least one bit	Not a hardware fault, but find out who forced what before you troubleshoot
STAT blinking green	Energy Pack is still charging	Normal for a few seconds after power-up
STAT off	Energy Pack isn't connected	Check the Energy Pack and its cable
STAT solid red	Energy Pack circuit fault	Replace the Energy Pack
STAT blinking red	Energy Pack is near end of life	Plan a replacement soon, before it fails during a power loss

Emerson's CPE305 guide notes two rare power-up conditions. A 9-1-1-15 blink code clears by power-cycling with the Energy Pack disconnected. All status lights blinking in unison indicates an over-temperature condition and also calls for a power cycle. If either keeps coming back, treat it as a hardware problem.

VersaMax LEDs and diagnostics (IC200)

VersaMax CPUs (IC200CPU001, CPU002, CPU005, CPUE05) and I/O modules (such as the IC200MDL650 and IC200ALG240) each have their own status LEDs. Descriptions follow the VersaMax PLC User's Manual (GFK-1503C).

What you see	What it means	Likely next step
CPU PWR off	The CPU isn't receiving 5V from the power supply	Check the power supply and its connection
CPU OK off	The CPU failed its power-up diagnostics	Power-cycle once. If OK stays off, the CPU likely needs repair or replacement
CPU OK blinking fast / slow	Running diagnostics (fast) or configuring I/O modules (slow)	Normal during startup; a problem only if it never settles
CPU RUN amber	Stop/IO Scan mode	The CPU is stopped but still scanning I/O
CPU FAULT on	Stop/Faulted mode from a fatal fault	Read the fault table
CPU FORCE on	An override is active on a bit	Not a hardware fault, but clear it before troubleshooting
I/O module OK off	The module isn't getting backplane power from the VersaMax power supply	Reseat the module and check the carrier. If OK stays off, the module has likely failed
I/O module Field Power off	No external field power to the module	Check field wiring and the field supply before replacing the module

Common VersaMax diagnostics

Loss of module: a module that was configured is no longer seen. If reseating doesn't fix it, suspect the module or the carrier base.
Extra module: an unconfigured module is installed, or a module after an empty slot can't be configured. VersaMax modules after an empty slot are left unconfigured.
Configuration mismatch: the module in a slot doesn't match the configured type. This is common after a replacement with the wrong part number.

Can't connect, or lost your program?

Some of the most common GE PLC questions aren't about a fault light at all. The programming software won't connect, or the program has disappeared. These are frustrating, but they often don't mean anything is broken.

"Unable to go online" or "Failed to establish connection to the controller": usually a communication problem, not a failed CPU. Check the cable or network connection, the IP address in your software, and the Ethernet module's LEDs. If Ethernet won't connect, try the CPU's serial port.
Error 8503 (Proficy Machine Edition): the connection timed out or dropped. Ping the PLC, check that the Ethernet module isn't faulted, and restart the software. An Ethernet module that keeps losing its settings may need repair or replacement.
Error 8533, "Unable to start runtime": the controller is in Stop/Fault mode. Check the PLC fault table to find out why it stopped (see the sections above).
Error 8544, "Flash operation failed": the software couldn't save to the CPU's flash memory. First confirm that your CPU model can save to flash. If it can and the error keeps happening, the memory may be failing.
Program lost after a power cycle (RX3i): if the logic shows "not equal" after power returns, check the Energy Pack first (the STAT LED above), and store your program to flash so it survives a power loss.
Program lost after a power cycle (Series 90-30): almost always a dead backup battery. Reload the program from your backup and replace the battery.

Not sure which one you're dealing with? Send us the exact error message. We'll help you work out whether it's a setting, a cable or a part.

Warning signs a module is failing

Not every failure comes with a clear code. If you're seeing any of these, take a closer look, and give us a call before it turns into unplanned downtime:

The same fault keeps coming back after you clear it, especially "Loss of" or "Addition of" module faults on the same rack and slot.
Intermittent faults that show up when the machine is idle, warm or vibrating, then disappear.
The battery light returns soon after a new battery. This usually points to the power supply, not the battery.
The CPU drops out of RUN with no program change, or a watchdog timer fault repeats.
I/O points don't match reality: an input LED is on but the program doesn't see it, or an output is commanded but nothing turns on.
Analog readings drift or freeze while the field device checks out fine.
Physical signs: heat discoloration, a burnt smell, bulging capacitors, or corrosion on pins and connectors.
Age and environment: modules in hot, dusty or high-vibration cabinets fail sooner. Many Series 90-30 and 90-70 systems have been running for decades and are past GE's end of life.

Repair or replace?

The honest answer: the right choice is whatever gets you running again without spending more than you need to. Sometimes that's a repair, sometimes a replacement part, and sometimes nothing at all.

Choose...	When...
A replacement part	The line is down and you need it running now. You have no spare on the shelf. The fault followed the module when you moved it to another slot.
A repair	You have a spare installed and can wait for the original. The part is hard to find or expensive. You want to rebuild your spare inventory.
Neither yet	The fault cleared after you reseated the module or replaced the battery. Field wiring or field power hasn't been ruled out. The fault came from a configuration or program change.

Once a part is back in service, keep a spare for your most critical modules (CPU, power supply, network interface) on the shelf, and keep a current program backup.

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