Omron CP1H backup battery
Part: CPM2A-BAT01
Battery part cited for CP1H BKUP and memory-retention faults.
$12-$35
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Omron CP1H PLC Error Codes
The Omron CP1H is a compact PLC that indicates faults through front-panel LEDs, the CX-Programmer error log, and system flags. Unlike CNCs or VFDs, Omron CP1H faults are often described as fatal or non-fatal errors rather than simple numeric alarms.
Front Panel Indicators
| LED | Meaning |
|---|---|
| PWR | Power present |
| RUN | Program executing normally |
| ERR/ALM solid | Fatal error, CPU stopped |
| ERR/ALM blinking | Non-fatal error, CPU still running |
| INH | Interrupts disabled |
| BKUP | Battery low or memory backup issue |
Common CP1H Faults
| Fault | Meaning | Typical Fix |
|---|---|---|
| Memory error | Program or DM memory corrupted | Re-download program, check battery |
| I/O bus error | Expansion module missing or failed | Reseat module, verify addressing |
| Battery error | Backup battery low | Replace battery with power on |
| Cycle time over | Scan time exceeded configured maximum | Optimize logic, increase cycle limit |
| Syntax/program error | Invalid instruction or bad jump | Compile in CX-Programmer and fix rung |
| Unit number duplicate | Smart units or option boards share address | Change DIP/unit number |
| PLC Setup error | Parameter mismatch after download | Rewrite settings and cycle power |
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Reading Faults in CX-Programmer
- Go online with the PLC
- Open PLC → Error Log
- Read the current and historical fault entries
- Note whether the error is marked Fatal or Non-fatal
Fatal faults stop the CPU. Non-fatal faults usually allow continued execution but indicate something needs repair.
Battery Fault
The CP1H uses a backup battery to preserve memory and clock data. If the BKUP indicator turns on:
- Replace the battery soon, ideally with the PLC powered on
- Omron battery part commonly used: CPM2A-BAT01 or equivalent for supported units
- If the battery fully dies on some configurations, clock and retentive memory may reset
Expansion I/O Faults
The CP1H can use digital and analog expansion modules. Common problems:
- Module not fully seated on side bus connector
- Broken DIN rail causing flex in the rack
- Wrong module declared in program comments/setup
- Analog module channel open circuit
If ERR/ALM blinks after adding an expansion card, remove the new card and confirm the CPU returns to normal.
Cycle Time Overrun
If the program scan exceeds the configured maximum cycle time, Omron logs a cycle time error. This happens after:
- Adding heavy math instructions
- Large loops or indirect addressing
- Excessive serial communication inside scan
Fixes:
- Review the cycle time in CX-Programmer diagnostics
- Reduce unnecessary loops
- Move communication to scheduled intervals instead of every scan
- Increase the allowed cycle time if appropriate
Clearing Errors
After fixing the cause:
- Clear the error log in CX-Programmer
- Power cycle or switch the PLC back to RUN mode
- Confirm ERR/ALM light stays off
Bottom Line
Most CP1H faults fall into four buckets: memory, battery, I/O expansion, or program timing. Start with the LED state, then read the error log in CX-Programmer for the real answer.