Omron CP1E ERR/ALM LED: fatal vs non-fatal error

• Solid: fatal error. The CPU stops executing the program. It is usually a memory error, a fatal error raised by the program itself or a unit failure.
• Flashing: non-fatal error. The program keeps running. This covers battery errors, communication errors and errors the program raises on purpose.
• A depleted battery on the models that have one, by far the most common cause of flashing.
• An error in the unit configuration or in the communication option board.
• A scan cycle that exceeds the configured watchdog time.

1. 1Observe the indicator before resetting. Solid and flashing lead to different diagnoses, and a reset erases the difference.
2. 2Connect with CX-Programmer or whatever programming software you use and read the CPU error area. That is where the code the front panel does not show lives.
3. 3If it flashes and the machine keeps working, check the battery and the internal clock date first. It is the most common cause and the cheapest.
4. 4If it is solid, check the unit power supply and the state of the option boards before suspecting the CPU.
5. 5Record the code you read along with the time. Without that, the next shift starts the diagnosis from zero.

Work on an energized panel: apply lockout/tagout and follow your plant procedure. This sheet guides the diagnosis, it does not replace it, and the manufacturer manual overrides anything written here.