A TM2424 that still answers communication requests but reports PLC ID 00 may have corrupted EEPROM contents. The observed sequence was loss of interface monitoring, an IR* response of IR00, and an unexpected password prompt when reloading a program that had no configured password.
Identify the Failure State
| Observation | Engineering interpretation |
|---|---|
| No communication error, but monitoring fails | The link is responding, so distinguish a configuration or memory problem from a completely dead communications path. |
IR* returns IR00
|
The PLC is reporting ID 00; attempt to restore the ID before clearing memory. |
| An unconfigured password is requested | Treat the password state as another indication of corrupted PLC memory. |
The available evidence does not establish the 4 ft ribbon cable or the 24 V switching power supply as the direct cause. Inspect those items, but use the ID and power-cycle tests below to determine whether EEPROM corruption or damage is present.
Restore the PLC ID and Clear Memory
- Use the existing change-ID command to change the PLC ID from
00to01. - Issue
IR*and verify that the returned ID is01. - If the ID changes successfully, execute the following command to clear the PLC program and remove the unexpected password state:
@01$cKILL00*Clearing memory removes the resident program, so retain a known-good program copy for the subsequent transfer. If the PLC cannot retain the change to ID 01, treat the EEPROM as damaged rather than merely corrupted.
Reload and Test EEPROM Retention
- Transfer the known-good program back to the PLC.
- Confirm that the program operates before removing power.
- Turn PLC power off and then on.
- Verify that the program loads correctly from EEPROM and operates after the power-on reset.
If the program survives the power cycle, the EEPROM was likely corrupted but remains usable. If the PLC loses the program again after power is restored, the M2017P EEPROM may be damaged and require replacement. The optional M2018P EEPROM was identified as an alternative that provides additional program and data EEPROM memory.
Reduce the Risk of Recurrence
Check whether the switching power supply has AC-line filtering and verify that surges are not reaching the PLC supply. The evidence specifically recommends an AC line filter to prevent power-surge energy from propagating through the supply and damaging the EEPROM. Also inspect the ribbon-cable connections, but do not replace the cable solely because it is 4 ft long; no cable-length failure was established.
FAQ
Why does a TM2424 return IR00 but show no communication error?
The PLC is responding to IR*, but it is reporting ID 00. Restore the ID to 01, retest with IR*, and then address the corrupted memory state.
How do I clear an unexpected TM2424 password?
After successfully changing the PLC ID to 01, execute @01$cKILL00*. This clears the PLC program and the password state, after which you must reload the known-good program.
How can I tell whether the M2017P EEPROM is damaged?
Reload the program, cycle PLC power off and on, and verify program retention. If the PLC loses the program again after the power-on reset, the M2017P EEPROM may be damaged; successful retention indicates that it was likely only corrupted.
