Schneider DFJ 5: Schneider Modicon M340 Error Code DFJ 5

Symptoms

The PLC STATUS LED turns red. The controller detects a memory fault. Internal RAM or flash memory has failed a read/write operation or checksum verification.

Possible Causes

Battery-backed RAM failure
Flash memory wear or corruption
Memory access violation in user code
Power surge damaged memory hardware

Troubleshooting Steps

Step 1: Read the memory fault details in EcoStruxure Control Expert
Confirm the fault type and affected memory region
Step 2: Attempt to re-download the application to flash memory
Application downloads and verifies correctly
Step 3: Replace the controller battery if RAM is affected
New battery maintains RAM contents during power cycles
Step 4: If the fault persists, replace the controller CPU module
New controller has no memory faults

How to Reset

To reset: 1) Re-download the application. 2) Replace the battery if needed. 3) If the fault persists, replace the CPU. 4) Reset the application. Caution: Memory faults often indicate hardware degradation, so plan for replacement.

Common Replacement Parts

BMXXBATO200: Modicon M340 backup battery (Replace every 2-3 years to prevent data loss)

Frequently Asked Questions

Q: How do I know if the battery needs replacing?
The PLC will log a low battery warning before the battery fails completely. Replace the battery as soon as the warning appears to prevent RAM data loss.
Q: What happens if the flash memory is corrupted?
The controller cannot boot the application. You need to re-download the application from EcoStruxure Control Expert. If re-download fails, the flash memory hardware may be permanently damaged.

Schneider Modicon M340 Error Code DFJ 5